By Emily Ayscue Hassel and Bryan Hassel; first published on EdNext.

You’ve probably read an article with a headline like this. Why say it again? Because class-size reduction continues to be so seductive. Our own state of North Carolina is just the latest in which policymakers have succumbed, causing a political firestorm this winter. Here it’s Republicans, but Democrats have heard the same call elsewhere. We thought we’d remind policymakers why they need to avoid the temptation.

Unlike many education issues, this one isn’t just a matter of opinion. Florida spent billions on class-size reduction with no positive impact on student results. A statewide study of Connecticut elementary schools found no statistically significant impact of class sizes.

But we understand why the concept still ensnares people. Surveys of teachers and parents alike reveal a lot of support for it: It makes common sense that teachers can more easily succeed with smaller classes. And some rigorous research suggests that dramatically reducing class sizes from the typical low-mid 20s to the 13–17 range has a positive effect on student learning in the K–3 years. (There’s no strong evidence of the value of small classes in grades 4+).

Why don’t these findings translate into statewide results? The answer’s pretty simple: A large-scale reduction requires hiring massively more teachers, dipping deeper and deeper into the applicant pool. It also reduces the number of students who have excellent teachers—the ones who produce more than a year’s worth of student growth each year, necessary to close proficiency gaps and help students leap ahead.

Suppose K–5 Elm Street Elementary has 100 kids per grade. If it has class sizes of 25, it needs 24 teachers. To get to class sizes of 17—what it takes to get the benefits cited above—the school needs 36 teachers, or 50 percent more. If the school’s district needed to hire 300 teachers per year before, it needs to hire 450 now. So, it gets the 300 teachers it would have hired…and then dips 150 ranks lower into its applicant pool for the rest.

Ouch. Double ouch for hard-to-staff rural and urban schools that could not fill their teachings slots previously. Triple ouch for districts if the mandate isn’t fully funded by the state—they must scramble to pay for a reform that won’t put an extra dime in any current teacher’s pocket. Ouch, ouch, ouch.

In addition, if Elm Street is typical, it probably has about six excellent teachers among the 24. Those six teachers teach 25 students each, reaching 150 children total with terrific instruction. Under the new policy, they teach only 17 students each, for a total of 102.

Many apologies to the 48 students who otherwise would have had one of these great teachers! In all likelihood, few if any of the extra teachers the school brings in to meet the mandate will be as good as those six. The situation would be even worse in high- and moderate-poverty schools, which tend to have lower levels of teacher quality to start with than their more advantaged counterparts.

What a huge loss: As research consistently shows, teacher quality is the single most important school-based factor in student learning. According to the research, any value gained through smaller classes gets more than offset by the hit students take when many fewer of them have great teachers, and many more of them have ineffective teachers—ones who induce far less than a year’s worth of student learning growth.

On top of all that, class-size reduction is just enormously expensive. If states have that much extra money, research suggests many better ways to spend it. And teachers themselves are clear about where they’d like to see the money go. In one survey, 82.7 percent of teachers would rather have a $5,000 pay bump than see their schools spend the $5,000 to drop class size by two students. If policymakers want to help teachers, why not just give them the money directly?

States that do set class-size limits below recent averages should use the policy we proposed in Seizing Opportunity at the Top: waive limits in cases where a highly effective teacher is voluntarily in charge of more students’ learning, either directly or by leading a team. Evidence suggests that students with great teachers in charge make higher growth, and teachers who take on advanced roles like them, too.

Why limit students’ and teachers’ access to that?

Originally posted on EdNext.