A few years back, we had a poor experience with our son (he was 5 at the time) in the school at 7springs, PA. They spent more time inside than out on the snow, and it was extremely crowded. The following year, we took him with us on our then annual trek to Big Mountain, MT. The groups were small (4 in my sons group), they spent almost the entire day, save for a quick hot lunch, on the snow, they made it fun for the kids, and they got them out of the beginners zone just as soon as possible. The PA program was babysitting, while the MT program was truly 'ski school'. My son, as well as all of the other kids I saw, had a blast in the Big Mountain program. On the second day, they had a somewhat rare 'bluebird' day, and my son's instructor took the kids to the top, where they could see the peaks of Glacier National Park stretching off in the distance. It was all my son could talk about for weeks.
There are a couple of other nice things about Big Mountain. Most importantly, there is an enormous amount of terrain, suitable for all levels of skiers, and I've never seen a crowd. The locals are a friendly bunch, and the hill has a laid back vibe. Whitefish is a cool local town too, although not for the Bognar suit crowd. The only downside, is fog, and getting there. Can't help you with the former, although service via Delta through SLC pretty much takes care of the latter issue. You can also get there via Amtrak to Whitefish.
I keep hearing great things about the Alta school as well, and it looks like we might be heading there the first week of April.