Studies on the effects of class size have been conducted since the 1920's. Results have often been mixed, with some methods of instruction favoring small classes and others more effective in large classes. Class size does not seem to make a difference when instructional goals involve learning and comprehending factual information. Smaller classes have been found more effective when instructional goals involve higher level cognitive skills including application, analysis, and synthesis. Smaller classes provide for greater contact between students and faculty, which appears to be most needed for students with low motivation, those with little knowledge of the subject matter, or those who have difficulty grasping conceptual material.
Smaller classes are also more effective than large ones in affecting student attitudes.
In sum, the optimal size of a class depends on the instructional goals being pursued and factors related to the students themselves. D.C. Heath and Company.