Are Florida’s celebrated test-score gains caused by the state’s education tax credit program? Maybe. What is certain is that Florida’s education tax credit program significantly increases student achievement in public schools.

David Figlio, a respected economist at Northwestern University and the official researcher for Florida’s education tax credit program, has completed the most rigorous analysis of how a private school choice program impacts public school performance.

The achievement effects increase in relation to the availability and diversity of private schools near the school. Schools with the most to lose make bigger gains. The kicker? All this happened BEFORE any kids left their public school. The performance gain came from the THREAT of competition.

On average, student achievement increased 1 percent for every standard deviation increase in the concentration of private school competitors before any students even used the program.

In schools on the margin of getting Title I funds from their district — in other words, those with the most to lose from losing poor students — the increase was over 3 percent before any students left. That means schools that had a medium level of competition private schools would see a more than 6 percent rise in scores and at the highest levels of competition that would reach nearly 13 percent.

Elementary and middle school student performance increased about 1.5 percent. Again, that means a 3 percent gain for medium competition and over 6 percent at the highest level of competition. Six years in, the average gain in schools facing more competition doubled to about 2 percent.

These effects are being called small by many, including Figlio. But it depends on what you mean by small. Those minority 4th grade test score gains that have been celebrated; they constitute a 5 percent increase on the NAEP. The grade school and marginal Title I impacts start looking pretty big in this context. And remember, this program supports less than 1 percent of students. And it saves money. Just think of the possibilities as it grows and competition expands dramatically.

In addition, these measures don’t capture what the cumulative effect of the increased competition might be. Are these gains ratcheting up student achievement? Has the growth in the size of the program increased its impact on achievement? And will the most recent expansion, which has no near-term limit, boost public school student achievement even more?

Figlio is continuing to analyze the data and I eagerly await his next installments …