I previously wrote (in admonishing Bill Clinton for getting NOLA data wrong) that this CREDO chart was one of the most powerful charts on the sector:

The graph demonstrates how aggregate charter school performance would increase in Math (they also have a graph for reading) under 5 closure scenarios.

Scenario B involves closing all charter schools that achieve significantly less growth than traditional schools. Under this scenario, aggregate charter school performance in math would be a .08 effect size (in reading, charters would achieve a .05 effect).

The National Alliance for Public Charter Schools recently released 2014 growth data. The sector is growing at an insane 14%. Also interesting is this closure data. See below.

In 2014, 501 hundred charter schools opened and 223 closed. With 6,723 charter schools in the country, that’s about a 3.3% closure rate.

Now consider this table from CREDO:

It shows that about ~30% of charters perform worse than traditional schools.

So the extrapolation problem of the day is this: given current data on opening, closure, and performance – what do you expect the performance breakdown will be in five years?

Of course, you’ll have to make some assumptions on whether it’s high-performing schools that are growing, and whether it’s low-performing schools that are closing.

I’m off to a Mardi Gras parade now, but if I have time this weekend I might play around with a model.

If you do as well, shoot me over a spreadsheet.