One of the early signs that candidate Bill de Blasio was genuinely committed to city public schools was his promise to reduce class sizes.

Democrats and Republicans often to throw around buzzwords like "choice," "accountability" and "standards." Sometimes even the word "education" seems like a buzzword.

By contrast, a candidate who specifically supports smaller class sizes sounds like someone who knows what he or she is talking about. Reducing class size is one of a handful of reforms we know of that enhances the school experience for all kids, and helps reduce the achievement gap between the haves and have-nots.

Some policymakers dispute the large body of research that supports smaller class sizes, but one can't help notice that they often send their children to expensive private schools whose main selling point is -- you guessed it -- small classes.

So far, though, we've seen little progress on this issue.

The United Federation of Teachers reports that city elementary school class sizes have continued to increase for the sixth year in a row. The average second-grade class is 25.3 students per class, compared with 21.1 six years ago. This is not only a matter of parent preference, but also of law: In 2007, a state court ruled that in kindergarten through third grade, class size should not exceed 20.

Of course, de Blasio, the first mayor in years with a child in public school, hasn't had much time to solve this problem. But it's not only that the numbers are disturbing, but also the lack of policy action. In January, Chancellor Carmen Fariña described reducing class sizes as a "long term" goal for the city. With the average class now in violation of state law, change should come more quickly than that.

It's also troubling that there doesn't seem to be much pressure from the teachers union, as Chalkbeat, an education news website, recently reported. Are union leaders going soft now that they don't have Mayor 1 Percent to kick around anymore?

De Blasio deserves credit for understanding that many of the "reforms" advanced by his predecessor did not serve public education. It would be a shame if he missed the opportunity to try a more proven reform of his own.

Liza Featherstone lives and writes in Clinton Hill.