When the class size is too large, it is difficult for a teacher to relate personally to all the students. Thus, he is forced to adopt more of an impersonal approach. This could make students feel less engaged in the learning process. Another con is that it is more difficult for teachers to grade papers and provide feedback to students.
A 1978 study, "Meta-analysis of research on the relationship of class size and achievement," by Glass and Smith analyzed 80 other studies on class size and academic performance. The study found that a smaller class size leads to better academic performance. Also, this effect is most pronounced as the class size gets reduced to fewer than 20 students.
Educational Research Service has further reviewed more than 100 different studies on the subject of effective classroom size. This review adds some qualifications to the basic finding of a correlation between class size and academic performance. The correlation varies depending on factors such as the grade level, characteristics of the pupil, the teacher's methods of instruction and the subject taught.
Smaller class sizes tend to have the most impact on academic performance when it comes to teaching reading and arithmetic at the primary school level, according to the ERS review. Not only that, but smaller class sizes also tend to most benefit students who are poorer, as well as students from an ethnic minority group. One drawback to the review is that it did not differentiate between the studies based on methodology. Thus, some of the studies may not have been as well designed as the others, which means some of the conclusions may be tentative.