This report reviews the literature on cost–benefit analysis of elementary and secondary school investments. A range of investments are considered: policies such as improving teacher quality, reducing class and school size; programs such as pre-school, Head Start, grade retention, and other specific interventions; and reforms, such as school choice, accountability, and whole-school reform. With the exception of pre-school, we find that the economic evidence is extremely thin, with almost no cost–benefit ratios. Areas that may offer potential for further inquiry are teacher productivity, special education, and the educational needs of immigrant students.