M.L.
Lots of expert advice from Dr. Sears here, I think they would really help you a lot, not only for discipline tactics, but also teaching your child how to express himself without the aggression:
http://www.askdrsears.com/html/6/T060100.asp
he specifically talks about the pinching/hitting and hw to combat it here:
http://www.askdrsears.com/html/6/T063900.asp#T062400
Time out for his age can work, but it depends. Mostly, it's for removing him from the situation for a few moments so he can calm down and be redirected in a less angry way when he goes back to play.
In a larger nursery room with that many kids including infants, it's not possible to expect them to catch him and redirect him every time like you are able. Of course, it's ideal, but simply not possible. If a short time out is going to work for him in that setting, then by all means they should do it. That is my opinion anyways.