Eva Moskowitz with a very insightful op ed in the Washington Post about the cost of small class size:

That class size should be small is revered like an article of faith in this country. Its adherents include parents, education groups, politicians and, of course, the unions whose ranks it swells. In many states it is even required by law, which has led to millions of dollars in fines against schools in Florida and a lawsuit against New York City by its teachers union.

Yet small class size is neither a guarantor nor a prerequisite of educational excellence.

The worst public elementary school in Manhattan, 16 percent of whose students read at grade level, has an average class size of 21; PS 130, one of the city's best, has an average class size of 30. Small class size is one factor in academic success. The question, then, is whether the educational benefits of class-size reduction justify the costs.

Some proponents contend that because research shows reducing class size is beneficial, spending on this should be prioritized over anything that is unsupported by research. That's a neat rhetorical trick but unsound logic. The absence of research on, say, teacher salaries doesn't prove that we should pay the minimum wage to teachers to dramatically reduce class size. Research should guide spending decisions only if it measures the benefits per dollar of spending on all alternatives.

At Harlem Success Academy Charter School, where we've gotten some of the best results in New York City, some classes are comparatively large because we believe our money is better spent elsewhere. In fifth grade, for example, every student gets a laptop and a Kindle with immediate access to an essentially unlimited supply of e-books. Every classroom has a Smart Board, a modern blackboard that is a touch-screen computer with high-speed Internet access. Every teacher has a laptop, video camera, access to a catalogue of lesson plans and videotaped lessons.

Outfitting a classroom this way costs about $40,000, or $13,500 amortized over three years. That's how much New York charter schools receive per pupil annually, so we can afford this by just increasing class size by a single student.

Add just one more student per class schoolwide, and Harlem Success Academy I gets another $300,000 in total. With that, we can afford headhunters to find the best principals in the country, business managers to handle the non-instructional administration that would otherwise distract these great principals from driving high-quality instruction, ample professional development for teachers, museum trips for students, etc.

In other words, a 19th-century school can be transformed into a well-managed 21st-century school by adding just two students per classroom. Reducing class size is expensive because most costs vary with class size. Decrease a class from 25 to 24 students and you need to hire 4 percent more teachers as well as build and maintain 4 percent more buildings.

Obsession with class size is causing many public schools to look like relics. We spend so much to employ lots of teachers that there isn't enough left to help these teachers be effective.

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