Homework and performance for time-constrained students

Most studies of homework effectiveness relate time spent on homework to test performance, and find a nonmonotonic relationship. A theoretical model shows that this can occur even when additional homework helps all students because of the way in which variables are defined. However, some students are time-constrained, limiting the amount of homework they can complete. In the presence of time constraints, additional homework can increase the spread between the performance of the best and worst students, even when homework would reduce the spread in the unconstrained case.