Many studies show that reducing the size of classes, especially in the first years of elementary school, can positively affect student achievement. Research generally indicates that the greatest influence on achievement occurs when class size is reduced to fewer than 20 students. Reducing class size also improves teacher morale and increases the amount of class time devoted to instruction. Additionally, the positive effect of smaller class sizes in the early grades appears to follow students throughout their education; these students graduate and go on to post-secondary education at higher rates than their peers who experience larger class sizes.
Although studies suggest that all students benefit from reduced class sizes, the positive influence on achievement is strongest for minority students and students from high-poverty backgrounds. Despite these apparent benefits, there is also a body of research that suggests that reducing class size is not necessarily the most cost-effective investment available, and that greater gains may be obtained through investment in other areas of education reform.