Common sense and research both tell us that if all else is equal, smaller classes are good for students. Unfortunately, in urban education, all else is rarely equal, and a host of problems hinder efforts to attract top teachers. So reducing class size without addressing teacher quality more broadly is akin to continually adding pitchers to your bullpen without worrying about whether any of them can even throw a fastball. Which challenges should have higher priority? First, education faces what economists would call an "adverse selection" problem. That means students with stronger scores on national exams like the SAT and GRE are less likely to enter the profession in the first place - and more likely to leave it within the first few years. Cutting class size won't fix that, and could even make things worse as schools have to find more teachers Second, teacher pay is still overwhelmingly based on years of service and advanced degrees rather than specific skills, willingness to take on challenging assignments and performance. As a result, not only is teacher pay too low overall, but underperformers and high achievers basically earn the same. The United Federation of Teachers and the city are starting to take small steps to address that - but what's needed is a radical overhaul rather than tinkering. Hiring, placement and retention of teachers also need to change. The New Teacher Project has found that in districts including New York City, collective bargaining contracts complicate teacher hiring, placement and retention. And rather than receiving substantial mentoring and support, rookies are largely left to sink or swim on their own. Research is clear that good teachers matter more than small classes, and all of these problems are substantial obstacles to attracting and retaining top teachers. To get the most bang for the buck, teacher quality rather than quantity should be New York City's top priority right now.

Rotherham is co-director of the think tank Education Sector and a senior fellow at the Progressive Policy Institute. He writes the blog Eduwonk.com.

Originally published on April 30, 2006