If you look closely, they're actually not hard to find: inexpensive professional development opportunities for teachers that actually do make a real difference in student learning. Earlier this year, we covered an experiment that demonstrated that teachers are remarkably more empathic towards their students after completing just a brief 70-minute exercise. We also learned how pairing a highly skilled teacher with one who is struggling, even absent a formal curriculum, turns out to be more effective than a lot of higher priced PD models.

Now, we're offered new evidence that spending very little money giving teachers access to high-quality math lessons can yield big pay offs.

In a white paper from the National Bureau of Economic Research, Kirabo Jackson and Alexey Makarin describe a nice little experiment in which 119 math teachers were given access to a library of inquiry-based lesson plans that currently runs at a cost of $320 per teacher for the year. Teachers also received a few occasional email reminders about the availability of the resources and were reminded that they could collaborate on Edmodo with other teachers also using the lessons. That was it.

The results were remarkable. By the end of the year, the growth in student achievement among these teachers was on par with far more costly efforts, such as reducing class size by 15 percent or replacing an average-quality teacher with a great one.

A couple of interesting points: 

First, it was the lowest performing teachers who saw the greatest gains.

Second, there were some teachers in the experiment who didn't get the email reminders and, with that group, there were no gains at all.

There are also some important caveats to this small study, including a significant decrease in lesson downloads and usage over time, suggesting that teachers did not themselves appreciate their value enough to implement more of them.

You can check out the lessons used in the study on the Mathalicious website.