The most critical factor of class-size reduction is the great cost. It requires huge investment in basic requirements, such as building bigger schools with more classrooms. Smaller-sized classes means more classes which require more resources for teaching and more technical equipment. For example, Ehrenberg, Brewer, Gamoran and Willms (2001) found that the state of California has been spending more than $1.5 billion annually over the past several years to reduce class size to 20 or fewer for children in the four-to seven-years-old. However, they say that if smaller classes really work, the economic benefits could outrun the investment costs. Not only from the better-educated workforce but also from avoided medical costs of a healthier, more informed populace. Unemployment levels will neap and the costs for social aids will be less.
Many studies have been conducted concerning the class size issue in the United States. Recently, some brand new analyses of the results were made as well as various new initiatives for collecting fresh data like the Californian programme and a smaller one in Wisconsin (Ehrenberg et al., 2001). However, none of them can prove absolute advantage of the class-size reduction. For example, reviewing the existing data kept by the U.S. Department of Education showed that