In our sample of schools in western Kenya, for example, the median first grade class in 2005 (two years after the introduction of free primary education, and prior to the class size reduction program we exploit here) had 74 students; average class size was 83; and 28 percent of first grade classes had more than 100 students. These classes are also very heterogeneous: Many of the new students are first generation learners and have not attended preschools (which are neither free nor compulsory in Kenya). Students differ vastly in age, school preparedness, and support at home. These challenges are not unique to Kenya. They confront many developing countries where school enrollment has risen sharply in recent years: understanding the roles of tracking and peer effects in this context is thus particularly important.
Peer Effects and the Impact of Tracking: Evidence from a Randomized Evaluation in Kenya (pdf file) Esther Duflo1, Pascaline Dupas2, and Michael Kremer3, 4