In 2003, Chicago schools required students entering ninth grade with below-average math scores to take two periods of algebra. This led to higher test scores for students with both above- and below-average skills, yet failure rates increased for above-average students. We examine the mechanisms behind these surprising results. Sorting by incoming skills benefitted the test scores of high-skill students partially through higher demands and fewer disruptive peers. But more students failed because their skills were low relative to classroom peers. For below-average students, improvements in pedagogy and more time for learning offset problems associated with low-skill classrooms. In some cases, classrooms were not sorted, but below-average students took an extra support class simultaneously. Test scores also improved in such classes.
The final, definitive version of this paper has been published in American Educational Research Journal, 50(4), August 2013 by SAGE Publications Ltd./SAGE Publications, Inc., All rights reserved. © 2013