Class size does matter. Class size is one of the most studied education policies, and an extremely rigorous body of research demonstrates the importance of class size in positively influencing student achievement. This policy first reviews the research on class size. Special attention is given to the literatures in economics and related fields. It then documents the recent rise in class size and considers how to compare the effects of class size reduction with other commonly discussed policy alternatives. In addition, research shows that students in early grades seem to excel and preform better in smaller class sizes. This is very important especially with students who come into a class with background disadvantages, such as lacking the language being taught. This allows teachers to be more affective with their students, and the research shows that students at an early grade level excel and continue that pattern throughout their educational career as they move up through school in smaller