Should School Go All Year?

Check out this post at the New York Times that argues that summer vacation makes inequality in America worse.
From the article:

The entire issue tends to vanish from public debate, because the educated, affluent people who run the debate don’t particularly suffer from it. Summer vacation costs money, but prosperous parents are happy to spend it on their kids. And of course there’s the sentimentality factor.

What do you think? School is important — should it go for all 12 months a year?