In the context of widespread efforts to reduce school fees, an increasing share of the costs of schooling come in the form of school materials and opportunity costs. We evaluate the impact of an educational intervention in which a Kenyan non-governmental organization distributes school uniforms to children in poor communities. The NGO used a lottery to determine who would receive uniforms. We use winning the lottery as an instrumental variable to identify the impact of receiving a uniform. We find that giving a school uniform reduces school absenteeism by 44% for the average student, and 62% for students who did not previously own a uniform. The program also raised test scores for recipients by 0.25 standard deviations in the year after inception.