In this paper we study the prospect of improving student by lowering class size at the Kindergarten through third grade levels. Class size is often cited as a primary factor in student achievement; a student teacher ration of fifteen to one is often thought to be ideal. However, smaller classes and improved performance are primarily linked by conventional wisdom. We present and summarize evidence that this conventional wisdom is faulty.
Class sizes in public schools across the nation have fallen considerably in the past hundred years. However, at the national level there is no strong evidence that smaller class sizes have had the expected positive influence on student performance. We also conducted a cross-sectional analysis of class size and student performance in Arizona and discovered that while there is some variance in average class sizes across Arizona school districts, there is no relationship between class size and performance. This fact casts doubt on the notion that Arizona students will benefit from further reductions in class size.
We summarize findings from class size experiments conducted in Indiana, Nevada, and Tennessee. These experiments show very little (if any) benefits due to smaller class sizes. Moreover, any benefits that do accrue from smaller classes were later shown to fade by about one half when students are reintroduced to regular classes. We argue that the meager benefits in the Tennessee study, combined with the "fade out" effect, also imply that class size reduction in Arizona will have a negligible effect on student achievement.
This study also details the significant cost of reducing class size in Arizona. Using very conservative estimates of personnel and capital costs, we estimate that reducing class size from current state K-3 average to fifteen students per teacher all at once would cost a staggering $415 million. Continuing maintenance and personnel costs would average over $200 million per year in perpetuity. Even if smaller classes were phased in over a period of four years, the project would cost a total of $616 million by the fourth year. Over fifteen years, the phased-in costs would be roughly $3.25 billion. We contend that lowering class size may not provide enough benefits to justify its cost to Arizonans.
The study concludes by pointing out that class size reduction is a step backward in recent legislative efforts to make Arizona schools more autonomous; a move toward centralization in an era of decentralization.