In other words, should schools assign students to classes based on academic performance and ability or randomly assign them?
Researchers argue that tracking is bad because low performers benefit from having high performers in their classes, i.e., the “spillover effect.” Teachers argue that they are better able to tailor instructional practices and curriculum in classes that are more homogeneous. They point out that “differentiating instruction” in heterogeneous classes is taxing and often yields disappointing results.
A new NBER study argues that we should listen to the teachers. In “Peer Effects and the Impact of Tracking: Evidence from a Randomized Evaluation in Kenya,” researchers conclude,
After 18 months, students in tracking schools scored 0.14 standard deviations higher than students in non-tracking schools, and this effect persisted one year after the program ended. Furthermore, students at all levels of the distribution benefited from tracking. A regression discontinuity analysis shows that in tracking schools scores of students near the median of the pre-test distribution score are independent of whether they were assigned to the top or bottom section.
