This was somewhat a surprise for me, I had heard of the ban in NYC and had assumed that the evidence proved that aluminum bats were more dangerous, I should have known better, as pointed out by the Wall Street Journal:

Reasonable people can disagree on the relative merits of wood versus aluminum, but leave it to the New York City to conclude that government should decide this issue for everyone else.
The City Council recently outlawed all metal bats in the city's high school baseball games come September. Proponents of banning metal...claim that balls go faster when hit with metal bats. But this hasn't caused more serious accidents: Studies from the American Legion and Consumer Product Safety Commission found zero reason for alarm.

As for New Yorkers, the peril of getting beaned with a line drive is hardly the most pressing concern for city's kids. Little League Baseball leaves the choice of wood or metal up to its local chapters because it says "there are no facts-none at all-to support" the claim that aluminum bats are more dangerous. Even at the college level, where metal bats are common, baseball is among the safer sports, with serious injury rates roughly on par with women's volleyball.

The current campaign is headlined by a couple of sad accidents, but these cases were literally less than on in a million. Legislation by anecdote is a good way to end up with minimum sentencing guidelines for swimming after eating a sandwich...