A study tracking two decades of Massachusetts charter schools reveals that effectiveness varied dramatically across different periods. Geoffrey Kocks, an economist at MIT, examined lottery-based data from the state that pioneered the urban charter movement to understand how these schools performed over time.
Shifting Results Over Time
During the earliest period through 2014, charter schools consistently boosted student test scores. Each year of enrollment increased math scores by roughly 0.25 standard deviations, roughly equivalent to moving a student from the 50th percentile to the 60th percentile on state assessments.
What Drove the Decline
Two factors coincided with the drop in effectiveness. First, teacher qualifications declined in the charter sector. Fewer instructors held undergraduate majors in their teaching subject or held licenses in those areas, while the opposite trend occurred in Boston’s traditional public schools. Second, many founding leaders and long-serving principals left their positions during the years leading up to the decline, creating organizational instability.
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The student population at these schools remained largely unchanged in terms of race, income, and family background throughout the study period, ruling out demographic shifts as an explanation. He also examined whether traditional public schools were improving and thereby narrowing the gap, but found no substantial gains in district school performance during the relevant years.
While the study doesn’t directly analyze funding levels or teacher pay, anecdotal evidence suggests Boston’s traditional public schools raised compensation during this time, potentially making them more competitive in recruiting teachers.
Geographic Patterns and the Post-Pandemic Rebound
The most significant changes occurred in Boston-area charter schools. Schools outside Boston maintained relatively stable effects throughout the study period. Boston charters had performed best in the early years, experienced the steepest decline, and showed the strongest recovery after 2020.
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The study relies entirely on test score data. Future work will examine chronic absenteeism and other outcomes beyond academic measurements. Whether charter schools’ post-pandemic advantages extend to social-emotional development or attendance remains unexamined.
Applications to charter schools have declined from their early 2010s peak, though many schools remain oversubscribed. When restricting analysis to only the schools that were oversubscribed in both periods, the overall pattern of results held, confirming that the findings aren’t explained by changes in which schools had available seats.
The research shows that charter school effectiveness is not fixed. The sector requires constant evaluation and willingness to adapt quickly when practices stop working.
