We randomly assign more than 6,000 students from 150 primary schools in Bangladesh to work on math assignments in one of three settings: individually, in groups with random schoolmates, or in groups with friends. The groups consist of four people and are balanced by average cognitive ability and...

We randomly assigned 115 primary schools in Bangladesh to one of two settings: children studying in groups with friends and children studying in groups with peers. The groups consisted of four people with similar average cognitive abilities and household characteristics. While the achievement of...