I've been to a couple, they are pretty good and fairly price. I think if you go to Kings in Short Hills it is much more expensive but the classes are also good. I live in Old Bridge, I heard from a friend there's a cooking school in either Old Bridge or Manalapan off Texas Road though I can't opine on the quality yet.
If you are not averse to traveling into Staten Island, try carolscafe.com her restaurant is excellent and her classes are great. If you can travel into the City, ICE or the culinary institute on I think 23rd between 5th and 6th is good.