Impacts of Oversubscribed Boston Pre-K Programs through Middle School

THE BOTTOM LINE

What kind of Pre-K experience sets students up for lasting success?

This study finds that Boston Public Schools’ (BPS) Pre-K program leads to stronger middle school outcomes than other preschool options. Although differences in outcomes between BPS Pre-K participants and non-participants were small in the early elementary years, some benefits re-emerge in middle school, suggesting a “sleeper effect,” where Pre-K benefits become larger as students continue on their academic trajectory. 

BPS Pre-K participants were more likely to apply to competitive exam schools, which begin in 7th grade, take and pass Algebra I by 8th grade, and demonstrate better academic and behavioral outcomes.

THE STUDY

Boston uses a lottery system to assign seats in oversubscribed Pre-K programs, creating a natural opportunity to study the program’s impact. This study followed over 12,000 children whose families applied for BPS Pre-K between 2007 and 2010, and about a quarter of these students applied to programs that were oversubscribed. By comparing students who were randomly offered a seat (lottery winners) to those who were not offered a seat (lottery losers), researchers were able to make causal claims about the effects of attending BPS Pre-K on student outcomes from 4th through 8th grade. 

Because nearly all control-group children (those who were not offered a seat in BPS Pre-K) attended other preschool programs, the findings from this study don’t simply show that any preschool is better than no preschool. Instead, they show that the BPS Pre-K program produces stronger medium-term outcomes than other preschool options available to families. There were also effects on the kinds of schools children attended through 8th grade.  This suggests that a combination of the specific features of the BPS model, along with their K-8 schooling contexts, were the drivers of these longer-term gains. 

HOW THE BPS PRE-K MODEL COMPARES TO ALTERNATE OPTIONS

KEY FINDINGS

Compared to their peers, BPS Pre-K participants…

1. Showed greater engagement with rigorous academic opportunities in middle school.
   Students who attended BPS Pre-K were 14 percentage points more likely to apply to one of Boston’s three competitive exam schools, which begin in 7th grade. They were also 22.6 percentage points more likely to take and pass Algebra I by the end of 8th grade, positioning them for stronger high school math trajectories and broader postsecondary options.
2. Scored higher on the 7th-grade math assessment.
   Boston Pre-K participants have higher test scores beginning in fifth grade. BPS Pre-K participants scored significantly higher on 7th-grade math assessments than non-participants (effect size = 0.24 SD).
3. Had fewer disciplinary incidents in 7th grade.
   Boston Pre-K participants are less likely to be suspended than non-attenders in 6th and 7th grades.  Students who attended BPS Pre-K had 7.6 percentage points lower suspension rates in 7th grade than their peers who did not attend the program.
4. Had higher student retention and school system stability
   BPS Pre-K participants were more likely to remain enrolled in BPS through middle school, less likely to switch schools at major transition points (such as 6th grade), and less likely to enroll in charter schools, compared to non-participants.

POLICY IMPLICATIONS

1. Effective Pre-K should include investments in teacher quality, instructional materials, and professional development. Boston’s Pre-K model included key features rarely found across the broader early childhood landscape: well-compensated and highly educated teachers, evidence-based language, literacy, and math curricula with a scope and sequence, and strong coaching and instructional support systems. The long-term gains observed in this study reflect those high-quality features, not just Pre-K participation alone.
2. Pre-K can have impacts on middle school outcomes. When evaluating Pre-K outcomes, policymakers should look beyond early test scores to outcomes like middle school coursework and behavior. This study shows that benefits such as higher 7th-grade math achievement and lower suspension rates can re-emerge later, even if early academic gains appear to fade in elementary years.
3. Districts facing enrollment declines or high mobility can use public Pre-K as a gateway to long-term engagement. Students who attended BPS Pre-K were more likely to stay in the district, suggesting that high-quality Pre-K may build trust and stability in the K–12 system.
4. Tracking course access, not just test scores, can reveal how Pre-K supports equity. BPS Pre-K participants were more likely to take Algebra I by 8th grade and apply to selective schools, showing that high-quality Pre-K influences long-term engagement with advanced coursework.

FULL WORKING PAPER

This summary is based on the EdWorkingPaper “Impacts of Oversubscribed Boston Pre-K Programs through Middle School,” published in May 2025. The full research paper can be found here:  https://edworkingpapers.com/ai25-1194