As thousands of parents have learned the last few months, teaching is deceptively complex. Some of the essential skills can be learned from textbooks and lectures—but knowing how to put it all in motion requires some real-world practice.

A forthcoming study from Dan Goldhaber, John Krieg, Natsumi Naito, and Roddy Theobald illustrates just how important it is for aspiring teachers to be assigned a genuinely effective cooperating teacher during student teaching—and makes the case that there are enough great teachers to go around.

They find that the most important factor when it comes to placing a student teacher is to find a cooperating teacher who is more effective than most teachers (based on the cooperating teacher's value added score), more so than placing a student teacher in a 'strong' school or in a placement that is a good match (such as placing a special education teacher candidate in a special education classroom—more on this in a future blog post). While all three of these are beneficial to future effectiveness, it is the opportunity to train under a great teacher that yields the greatest benefit.

To put this into perspective, the difference in outcomes for a student whose teacher trained under an above-average cooperating teacher versus an average one is equivalent to the difference in outcomes for a student taught by a veteran teacher versus a brand new one. Those are big differences.

Given the magnitude of this finding, both teacher preparation programs and school districts need to pay more attention to the quality of the teacher. Our own research finds that only 13 percent of prep programs require the cooperating teacher to be demonstrably effective.

Many prep programs and districts claim they can't get the best teachers to volunteer to take on a student teacher. Goldhaber et al. demonstrate that at least in Washington state, there are enough great teachers to mentor every student teacher in the state. Convincing those great teachers to sign up is more of a challenge.

That's where a good-sized honorarium should come in. The researchers suggest that effective cooperating teachers are worth a lot, but that a $500 incentive just isn't sufficiently persuasive—and many districts do not offer their cooperating teachers even that much, if they offer any incentive at all.