Impact of bilingual education on student achievement

This article discusses the impact of bilingual education on student achievement. Recent studies suggest that bilingual education programs and English-only programs are not significantly different in their impact on standardized test performance. The article highlights the pros and cons of bilingual education and emphasizes the need to focus on the quality of instruction rather than the language of instruction. The article also provides empirical evidence on the impacts of bilingual education.

Aimee Chin
University of Houston, USA, and IZA, Germany
Impact of bilingual education on student achievement. IZA World of Labor 2015: 131
doi: 10.15185/izawol.131| Aimee Chin ©| March 2015| wol.iza.org 11
AUThOR’S mAin meSSAGe
Discussions about how to educate limited English proficient students often focus on the language of ins
However, convincing recent evidence that bilingual education programs and English-only programs in U
schools are similarly effective in their impacts on student achievement suggests that it could be more
to shift the focus from the language of instruction to the quality of instruction. Instruction should be of
intensity, provided by teachers qualified to teach limited English proficient students, and supported by
teaching and learning materials, regardless of the language of instruction.
impact of bilingual education on student
Language development programs should focus on quality rath
the language in which instruction is provided
Keywords:bilingual education, language of instruction, English as a second language, structured Englis
immersion, limited English proficient students, English language learners
Pros
Bilingual education may help limited English
proficient students keep up in other subjects
while they learn English.
Bilingual education helps limited English
proficient students develop language skills in
their native (non-English) language.
Skills in students’ native language may facilitate
their development of skills in English.
Bilingual education supports cultural inclusion
and diversity.
Cons
By reducing exposure to English, bilingual
education may slow the acquisition of English
language skills.
A shortage of certified bilingual education
teachers makes it difficult to implement
bilingual education programs as intended.
Appropriate teaching and learning materials
may not be available in all native languages.
Bilingual education segregates limited English
proficient students from other students, which
may have social and academic impacts.
KeY FinDinGS
eLeVATOR PiTCh
More than 4.4 million students enrolled in US public
schools participate in English language learner
programs because of linguistic barriers to learning
in regular classrooms. Whether native language
instruction should be used in these programs is a
contentious issue. Recent studies, using credible
research designs for estimatingcausal impacts,
find that bilingual education programs (which use
some native language instruction) and English-only
programs are not significantly different in their impact
on standardizedtest performance.This finding
suggests that it is time to change the focus from use of
the native language to program quality.
Source: Author’s calculations based on data from Digest of Education
Statistics, 2013, Table 204.20. Online at: http://nces.ed.gov/programs/
digest/d13/tables/dt13_204.20.asp?current=yes
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
4.1
4.4
2.8
1.6
2.9
1.2
Millions of studentsƒ
2002 2003 2004 2005
All states Top 6 states Other states
2006 2007 2008 2009 2010 2011
Enrollment of limited English proficient students
public schools is large and growing, 2002–2011

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Aimee Chin| Impact of bilingual education on student achievement
mOTiVATiOn
Many children attend schools that teach in a language in which they are not proficient,
and this trend is growing due to rising international migration. Linguistic barriers to
learning in regular classrooms put these students at risk of poor education outcomes.
A variety of education programs are proposed to improve outcomes. Evidence on
their effectiveness can guide parents, educators, and policymakers. The US has many
limited English proficient students, and several rigorous evaluations of bilingual
education exist for US programs, which is why the US is the focus here.
Enrollment of limited English proficient students in US public elementary and secondary
schools (as measured by number of students participating in English language learner
programs) reached 4.4 million in 2011/2012, or 9% of total enrollment, and is growing
much faster (6.6% between 2002/2003 and 2011/2012) than enrollment of other
students (2.4%). Enrollment was flat in California, Texas, Florida, New York, Illinois,
and Arizona (the top six states by number of limited English proficient students) but
grew 29% in the other states over the decade, reflecting the increasing geograp
dispersion of immigrants. In 2011/2012, 74% of US public schools had at least one
limited English proficient student. Many schools are making decisions about how to
educate their limited English proficient students.
DiSCUSSiOn OF PROS AnD COnS
Scores on the grade 4 mathematics test on the National Assessment of Educational
Progress (the largest nationally representative assessment of what American students
know) show a persistent achievement gap between limited English proficient students
and other students (Figure 1). At 25 points, the gap is large (0.8 standard deviations)
and greater than the gap between poor and non-poor students. Other measures of
academic performance show a similar gap. Lower test scores indicate that limited
English proficient students are less proficient in core academic skills, which may make
later classes more difficult, cause placement in less rigorous tracks of study, and raise
dropout rates, lowering eventual educational attainment and human capital.
Because lack of proficiency in English is a barrier to learning in regular classrooms,
US civil rights laws require schools to offer additional instructional services to limited
English proficient students. Programs fall into two broad categories: those that use
the student’s native language for at least some of the instruction (bilingual education),
and those that use only English for instruction. As the emphasis of all these programs
is English language development, both programs devote time to this, typically using
English as a second language (ESL) methods. Also, there is considerable variation
in how much the native language is used in bilingual education programs. Thus, the
contrast between bilingual education programs and English-only programs is less
stark in practice than in theory.
Potential effects of bilingual education on student outcomes
Potential benefits of bilingual education
When limited English proficient students are still learning English, it may be better to
teach other subjects in their primary language. To the extent that the course content

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Aimee Chin| Impact of bilingual education on student achievement
is more accessible when taught in the native language, limited English proficient
students will not fall (as far) behind in these other subjects while they are catching up
in English.
Receiving instruction at school in the native language may also improve students’ skills
in their native language. Additionally, parents of limited English proficient students,
who themselves typically lack proficiency in English, may be better able to assess their
children’s school progress, help with schoolwork, and communicate with teachers in
a bilingual education setting.
Instruction in the native language might develop general language skills that facilitate
learning new languages. For example, some strategies developed for reading in t
native language may be applicable for reading in English.
Potential drawbacks of bilingual education
Because some instruction is in the native language, bilingual education students
receive less exposure to English at school than students in English-only programs
This might delay and weaken their acquisition of English language skills, which could
in turn affect the academic tracks they can pursue later.
Sometimes the inputs needed for bilingual education programs are not available.
First, it is difficult to recruit enough certified bilingual education teachers for some
districts, languages, and grades. While teaching in English-only programs also requires
special training, there is a larger pool of candidates since proficiency in a non-English
language is not necessary. Second, teaching and learning materials are not available in
many native languages, subjects, and grades. Thus, implementing bilingual education
programs as intended becomes more difficult.
Because bilingual education programs provide some content instruction in the native
language, limited English proficient students with the same native language and
Figure 1. Grade 4 mathematics performance on the National Assessment of Educational
Progress, by limited English proficient and low-income status
Note: Poor students are defined as those who are eligible for the National School Lunch Program.
Source: Author’s calculations based on data from National Center for Education Statistics, National Assessment of
Educational Progress Mathematics Assessments, various years.
Online at: http://nces.ed.gov/nationsreportcard/naepdata/
260
240
220
200
180
160
140
120
1995 1997 1999
Limited English proficient
Not limited English proficient
Not limited English proficient and poor
Not limited English proficient and not poor
2001 2003 2005 2007 2009 2011 2013
Scaled score

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Aimee Chin| Impact of bilingual education on student achievement
the same grade tend to be grouped together in self-contained classrooms, unlike in
most English-only programs. On average therefore, limited English proficient students
placed in bilingual education programs have less exposure to other students as well
as to limited English proficient students of other native languages, and there could be
peer effects associated with this.
Who receives bilingual education?
Although more than 200 home languages are reported among limited English proficient
students in US public schools, in practice bilingual education programs are available
only for a few languages, with Spanish–English programs by far the most common. This
is primarily because Spanish-speaking limited English proficient students are the most
numerous (they made up 77% of limited English proficient students in 2001/2002; the
next largest group was Vietnamese speakers, at 2.4%) [1]. Moreover, Spanish-speaking
limited English proficient students are more likely than other limited English proficient
students to be placed in bilingual education programs: 38% compared with 17% [1].
This highlights that student placement in bilingual education is not random. Whether
a student participates in bilingual education depends on many variables, including
characteristics of the student (such as home language, grade, English proficiency
parents (such as income, education, whether they take up the program if it is offered
to their child), neighborhood (such as community preference for bilingual education,
having enough limited English proficient students with the same native language and
in the same grade), and state (some states mandate bilingual education while some
ban it). Researchers do not have data on all the variables that affect participation,
and because some of these variables also affect student achievement, conventional
estimates of participation in bilingual education will suffer from omitted variables
bias. Besides the problem of non-random selection into bilingual education, there are
also complications in measuring education outcomes for limited English proficient
students. Thus, estimating the causal impact of bilingual education on student
achievement is a challenge.
empirical evidence on the impacts of bilingual education
Studies can be cited to support either side of the debate on whether bilingual education
programs work better than English-only programs; early meta-studies are [2], [3]. Many
of the studies fail to deal with the non-random selection of limited English proficient
students into bilingual education programs. Students who participate in bilingual
education are systematically different in observed and unobserved characteristics
from students who do not, so the achievement difference between participants and
non-participants could not be causally attributed to bilingual education. In addition,
some of the studies are limited in sample size or several decades old. In the pa
few years, however, several large-scale studies have used experimental or quasi-
experimental methods to obtain convincing estimates of causal impact.
Evidence from a recent randomized experiment
A recent study that randomly assigned limited English proficient kindergartners in six
schools to bilingual education or structured English immersion finds no statistically

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Aimee Chin| Impact of bilingual education on student achievement
significant differences in English skills by grade 4 as measured on standardized tests
[4]. In earlier grades, though, difference in English test scores between students in
the two programs were larger and sometimes statistically significant. In grade 1, the
deficits for bilingual education students were over one-third of a standard deviation
and statistically significant. By grades 2 and 3, the deficits had diminished, and only
two of the eight scores (four for each grade) were statistically significant. On th
other hand, in all four grades, students randomly assigned to bilingual education had
significantly better performance on the tests measuring Spanish skills.
The treatment effects, estimated as far out as five years after the randomization of
treatment status, are not confounded by attrition bias as the attrition rate, and the
baseline test scores of those who left the study, did not differ significantly between
students in bilingual education and those in structured English immersion. Thus,
althoughstudentsin bilingualeducationinitially had worse English skills than
students in structured English immersion programs, their later English skills did not
differ significantly [4].
These estimates of the causal impact of bilingual education relative to structured
English immersion have internal validity, but external validity is limited by the small
number of students and schools. Thus, it is of interest to look at studies coverin
more students and in other contexts.
Data challenges in measuring the education performance of limited
proficient students
High-performing students exit limited English proficient status sooner. Students are placed
mainstream classes when their academic performance is sufficiently high. Thus, the
achievement gap with other students can be expected to widen over time as better
performing students exit and lower performing students remain in the sample. With
access to student longitudinal data, researchers can determine whether a student
has ever been in limited English proficient status and not have to rely on the current
limited English proficient status.
Limited English proficient students are more likely to drop out of school than other student
lower performing students are even more likely to drop out, so the measured achie
of limited English proficient students in upper grades may overestimate the true
performance of that cohort. Ideally, researchers should examine dropout behavior
along with test performance.
Under federal law, limited English proficient students can be exempted from state assessm
in their first year of enrollment and in later years can be offered test accommodations (suc
taking content tests in their native language). Thus, researchers measuring student
performance using scores on standardized exams should consider potential selection
into the exam pool and the comparability of exams administered in different languages.
Population surveys include data on limited English proficient individuals who never attende
schools. Data from nationally representative surveys of the US population can be used
to examine adult outcomes (such as educational attainment and wages). Many limited
English proficient adults in these data sets are migrants who arrived in their teens and
later and never attended US schools, which limits the ability to link education or wage
gaps observed in these data to US school policies.

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Aimee Chin| Impact of bilingual education on student achievement
Evidence from analyses of the impact of policy changes
The official evaluation of Proposition 227, a California voter referendum banning
bilingual education,finds that the share of limited English proficientstudents
receiving bilingual education dropped from 30% in 1997/1998 (the last year before
implementation)to 8% in 2003/2004,with limited English proficientstudents
shifting to structured English immersion programs [5]. A comparison of the change
in mathematics and reading test scores for limited English proficient students with
the change for students who had never been identified as limited English proficient
(difference-in-differences analysis) finds a small, statistically insignificant change in
the gap between the groups.
Under the assumption that in the absence of the policy change, the gap would have
been unchanged, this finding suggests that bilingual programs are as effective as
English-only programs for limited English proficient students. However, the authors
point out that there were other policy changes around the same time that might make
the assumption less plausible, including changes in national accountability standards
(such as fewer exemptions from state assessments) and the introduction of the
California English Language Development Test in fall 2001 to measure the Englis
proficiency of limited English proficient students. It is likely that these other policy
changes affected limited English proficient students and other students differently
making it difficult to disentangle the effect of Proposition 227 from these other
changes using a difference-in-differences method with non-limited English proficient
students as a comparison group.
Two other studies also use Proposition 227 to learn about the effect of bilingual
education, but with a different comparison group. Their insight is that schools
in California with a higher prevalence of bilingual education before Proposition
227 would have to move a larger share of limited English proficient students ou
of bilingual education to comply with the ban on bilingual education than would
schools with lower prevalence. Comparing changes over time for limited English
proficient students in schools with higher pre-policy prevalence to changes in schools
with lower prevalence gives an alternative difference-in-differences estimate of th
impact of a reduction in bilingual education. Since this analysis uses data on limited
English proficient students only, other policies that differentially affect limited English
proficient students are controlled for (because everyone, even the comparison group,
is exposed to them).
One study using 1990 and 2000 US Census microdata finds that Proposition 227
increasedthe self-reportedEnglish-speakingability of children aged 5−18who
immigrated to the US within the past three years from a non-English-speaking country,
who are likely to be placed in programs for limited English proficient students [6]. The
post-policy year of 2000 is only two years after Proposition 227 was implemented, so
the finding is consistent with English speaking ability developing faster when children
are placed in structured English immersion instead of bilingual education programs.
Left unanswered are impacts on academic English skills and longer-term English
language skills.
The other study uses scores from the California English Language Development
Test, a richer measure of English proficiency [7]. Because these scores were available
beginning only in 2001, there are no pre-policy data; however, the broad intuitio

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Aimee Chin| Impact of bilingual education on student achievement
behind the empirical strategy is similar. It uses the change in a school’s bilingua
education prevalence predicted by perfect compliance with Proposition 227 as an
instrumental variable for a student’s actual participation status in bilingual education
and controls for a rich set of school characteristics to address the concern that
schools with higher and lower pre-policy bilingual education prevalence rates differ
systematically. For Spanish-speaking limited English proficient students in grades
1 and 2, bilingual education, relative to English-only approaches, has significant
large negative associations with English listening and speaking proficiencies, but
the associations are small and positive in grades 3–5 (and insignificant in grade 5).
English reading and writing proficiencies are measured in higher grades, and there is
no evidence of significant differences in grade 5, with mixed results in grades 3−4.
instrumental variable approach
Ordinary least squares estimates of the effect of an intervention on the dependent
variable may not have a causal interpretation due to such concerns as omitted
variables bias and reverse causality. If there is a variable that is both correlated
with the intervention variable and affects the dependent variable only through the
intervention variable, this variable can serve as an instrumental variable. It can be
used in place of the intervention variable to estimate the local average treatment
effect (local to individuals whose intervention status is affected by the instrument).
Massachusetts voters passed a similar initiative banning bilingual education beginning
in 2003/2004. A difference-in-differences analysis compares the cohort difference
(between the post-policy cohort that took the grade 3 Massachusetts Comprehensive
Assessment System exam in spring 2006 and the pre-policy cohort that took the exam
in spring 2003) for limited English proficient students with the cohort difference for
students who had never been identified as limited English proficient students [8]. The
study finds small, statistically insignificant differences in reading scores. The finding of
no effect of the policy reducing bilingual education holds for both Spanish-speaking
and other native language-speaking limited English proficient students.
Evidence using policy rules
Texas requires school districts to offer bilingual education when 20 or more limited
English proficient students are enrolled in a particular grade and speak the same
native language. A study using a regression discontinuity design exploiting this policy
rule finds no statistically significant difference in state standardized mathematics
and reading test scores for grade 3–5 students whose native language is Spanish in
districts that are above the 20-student cutoff (more likely to be exposed to bilingual
education) and those in districts that are below the cutoff (more likely to receive only
ESL instruction) [9]. Since most of these students would have been limited English
proficient students in an earlier grade, this finding suggests that bilingual education
programs and ESL programs, as implemented in small, less urban schools in Texas,
have similar impacts on later student achievement. However, these effects of bilingual
education may not necessarily generalize to larger, more urban districts or to limited
English proficient students whose native language is not Spanish.

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Aimee Chin| Impact of bilingual education on student achievement
Regression discontinuity design
When a policy specifies cutoffs for determining eligibility for an intervention, a
regression discontinuity design can be used to estimate the causal impact of the
intervention. Suppose assignment to an intervention is made if an underlying variable
exceeds some threshold value. Individuals just above and just below the threshold are
expected to be the same in all ways except for the intervention. Comparing outcomes
for those above and below the threshold gives an estimate of the local average
treatment effect (local to individuals near the threshold).
A study in a large north-eastern urban district also uses a regression discontinui
design to estimate the effect of bilingual education [10]. It finds little difference in
achievement between students who scored just below the English skills assessment
cutoff (and are eligible to participate in bilingual education or ESL programs according
to the district policy rule) and those who scored just above (ineligible and placed in
mainstream classrooms) [9]. Thus, instruction that uses some native language is no
more effective than the all-English instruction occurring in mainstream classrooms.
Because the study focuses on students near the cutoff score, the results for the impact
of limited English proficient programs apply only to the most English-proficient among
limited English proficient students.
Evidence outside the US
A few studies estimate the effect of changes in language of instruction policies.
Morocco, a reform that changed instruction from Arabic in grades 1–5 and French in
grades 6–12 to Arabic only is found to decrease French writing skills but not to affect
French reading, Arabic, and mathematics skills [11]. In Latvia, a reform that changed
instruction from Russian only to 60% Latvian and 40% Russian in secondary schools
lowered the high school exit exam scores of ethnic Russians [12]. In South Afric
instruction is in the native language in early grades, and English or Afrikaans in later
grades, and a reform increasing the grades providing native language instruction has
led to higher literacy and educational attainment [13]. These studies emphasize that
school quality changes are coupled with the changes in the language of instruction,
and all the studies find that student outcomes are better when quality is higher (which
is sometimes with native language instruction and sometimes not).
LimiTATiOnS AnD GAPS
There are several limitations and gaps in the work evaluating US bilingual education
programs. The studies discussed here reflect mainly the impacts of transitional
bilingual programs, the most common type in the US. However, their impacts may well
differ from those of programs that have bilingualism as a goal, such as maintenance
bilingual education and dual language immersion programs.
The literature focuses on English language skills and standardized test scores in
English and mathematics as outcomes. These are important in that the main goal of
limited English proficient programs is to help limited English proficient students to
close the achievement gap. However, it would also be of interest to measure a broader

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Aimee Chin| Impact of bilingual education on student achievement
Competing interests
The IZA World of Labor project is committed to the IZA Guiding Principles of Research
Integrity. The author declares to have observed these principles.
© Aimee Chin
set of outcomes, including native language skills, degree of bilingualism, non-cognitive
skills, high school dropout rate, and educational attainment.
A final limitation is that the literature focuses on impacts on limited English proficient
students and ignores the possibility that these education programs might have
spillover effects on other students. The one study that considers this possibility finds
that achievement for non-limited English proficient students is higher in districts that
began to offer bilingual education as a result of a Texas administrative rule [9]. While
this finding is consistent with non-limited English proficient students benefiting from
lower exposure to limited English proficient students, this interpretation is speculative,
and more research is needed on spillover effects.
SUmmARY AnD POLiCY ADViCe
Collectively, a set of recent studies using experimental and quasi-experimental variation
in exposure to bilingual education to estimate its causal impact suggests that while
receiving some instruction in the native language might lower English-language skills
initially, its impact on later English proficiency and achievement is not systematically
better or worse than that of English-only approaches. This finding does not mean
that school programs for limited English proficient students are not helpful—the
studies compare one type of limited English proficient program with another type,
not with no program at all. Rather, the implication is native language instruction is
not essential to program effectiveness. This may be because bilingual education and
English-only programs, as implemented in US schools, have more similarities than
differences—both focus on English language acquisition and both use English as the
main language of instruction. Moreover, this finding does not preclude the possibility
that some bilingual education programs might raise achievement among limited
English proficient students more effectively than English-only programs do—or vice
versa.
The national debate on how to educate limited English proficient students has
focused too much on language of instruction. It would be productive to shift the
focus to the quality of instruction [4]. Local communities should be able to choose
a program that can be staffed with qualified teachers, have appropriate teaching
learning materials, deliver an adequate number of hours per day of English language
development services, and meet broader community goals without first tying thei
hands about using or not using native language instruction.
Acknowledgments
The author thanks an anonymous referee and the IZA World of Labor editors for
many helpful suggestions on earlier drafts.

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Aimee Chin| Impact of bilingual education on student achievement
ReFeRenCeS
Further reading
August, D., and T. Shanahan. Developing Literacy in Second-Language Learners: Report of the Nationa
Panel on Language-Minority Children and Youth. Mahwah, NJ: Lawrence Erlbaum Associates Publishers
2006.
Cheung, A. C. K., and R. E. Slavin. “Effective reading programs for Spanish-dominant English
language learners (ELLs) in the elementary grades: A synthesis of research.” Review of Educational
Research 82:4 (2012): 351–395.
Key references
[1] Zehler, A. M., H. L. Fleischman, P. J. Hopstock, T. G. Stephenson, M. L. Pendzick, and S. Sapru.
Descriptive Study of Services to LEP Students and LEP Students with Disabilities, Volume IA Resea
— Text. Washington, DC: US Department of Education, 2003.
[2] Baker, K. A., and A. A. de Kanter. Effectiveness of Bilingual Educational: A Review of the Literature
Washington, DC: Office of Planning, Budget and Evaluation, US Department of Education,
1981.
[3] Willig, A. C. “Meta-analysis of selected studies on the effectiveness of bilingual education.”
Review of Educational Research 55:3 (1985): 269–317.
[4] Slavin, R. E., N. Madden, M. Calderón, A. Chamberlain, and M. Hennessy. “Reading and
language outcomes of a multiyear randomized evaluation of transitional bilingual education.”
Educational Evaluation and Policy Analysis 33:1 (2011): 47–58.
[5] Parrish, T., A. Merickel, M. Pérez, R. Linquanti, M. Socías, A. Spain, C. Speroni, P. Esra, L.
Brock, and D. DeLancey. Effects of the Implementation of Proposition 227 on the Education of Eng
Learners, K-12: Findings from a Five-Year Evaluation: Final Report. Palo Alto, CA: American Institu
for Research, 2006.
[6] Kuziemko, I. “Human capital spillovers in families: Do parents learn from or lean on their
children?” Journal of Labor Economics 32:4 (2014): 755–786.
[7] Jepsen, C. “Bilingual education and English proficiency.” Education Finance and Policy 5:2 (2010):
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[8] Guo, Q., and D. Koretz. “Estimating the impact of the Massachusetts English immersion law on
limited English proficient students’ reading achievement.” Educational Policy 27:1 (2013): 121–14
[9] Chin, A., N. Meltem Daysal, and S. Imberman. “Impact of bilingual education programs on
limited English proficient students and their peers: Regression discontinuity evidence from
Texas.” Journal of Public Economics 107:C (2013): 63–78.
[10] Matsudaira, J. D. Sinking or Swimming? Evaluating the Impact of English Immersion versus Bilingu
Education on Student Achievement. Berkeley, CA: University of California, 2005.
[11] Angrist, J., and V. Lavy. “The effect of a change in language of instruction on the returns to
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[13] Eriksson, K. “Does the language of instruction in primary school affect later labour market
outcomes? Evidence from South Africa.” Economic History of Developing Regions 29:2 (2014):
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The full reference list for this article is available from the iZA World of Labor webs
(http://wol.iza.org/articles/impact-of-bilingual-education-on-student-achievement)