Numerous studies have been done to assess the impact of class size reduction. Although most studies do show a relationship between small class size and increased student achievement, researchers disagree on how to interpret the results. Because there are so many variables in the average classroom — the quality of the teacher, the home environment of the students, the quality of the curriculum, the leadership of the school — it is difficult to draw definitive conclusions about student achievement based on class size alone. In other words, strategies effective in one setting may not be equally effective in another. Nevertheless, studies over a period of years have pointed to a number of trends as a result of lowering class size:
Gains associated with small classes generally appear when the class size is reduced to less than 20 students.
Gains associated with small classes are stronger for the early grades.
Gains are stronger for students who come from groups that are traditionally disadvantaged in education — minorities and immigrants.
Gains from class size reduction in the early grades continue for students in the upper grades. Students are less likely to be retained, more likely to stay in school and more likely to earn better grades.
Academic gains are not the only benefit of lowering class size. A recent study published in the American Journal of Public Health revealed that reducing class sizes in elementary schools may be more cost-effective than most public health and medical interventions. This is because students in smaller classes are more likely to graduate from high school, and high school graduates earn more and also enjoy significantly better health than high school dropouts.