Sorting Students?

http://www.nber.org/papers/w18848.pdf


Does Sorting Students Improve Scores? An Analysis of Class Composition
Courtney A. Collins and Li Gan
NBER Working Paper No. 18848
February 2013
JEL No. I21


This paper examines schools’ decisions to sort students into different classes and how those sorting
processes impact student achievement. There are two potential effects that result from schools creating
homogeneous classes—a “tracking effect,” which allows teachers to direct their focus to a more narrow
range of students, and a peer effect, which causes a particular student’s achievement to be influenced
by the quality of peers in his classroom. In schools with homogeneous sorting, both the tracking effect
and the peer effect should benefit high performing students. However, the effects would work in opposite
directions for a low achieving student; he would benefit from the tracking effect, but the peer effect
should decrease his score. This paper seeks to determine the net effect for low performing students
in order to understand the full implications of sorting on all students.

We use a unique student-level data set from Dallas Independent School District that links students
to their actual classes and reveals the entire distribution of students within a classroom. We find significant
variation in sorting practices across schools and use this variation to identify the effect of sorting on
student achievement. Implementing a unique instrumental variables approach, we find that sorting
homogeneously by previous performance significantly improves students’ math and reading scores.
This effect is present for students across the score distribution, suggesting that the net effect of sorting
is beneficial for both high and low performing students. We also explore the effects of sorting along
other dimensions, such as gifted and talented status, special education status, and limited English proficiency