We were also shut out. I asked someone there before the priority registration started, and she said the younger kids' camps often sell out quickly. Thought about paying the $300, but darn that's a lot for one week of camp, especially since I wasn't even sure DS would like it.
Same experience with the zoo camp -- the session we wanted sold out before it was even open to non-priority registration (and they said a couple of sessions even sold out within minutes of the priority registration opening). But, at least with the zoo, the priority access is only $120 (plus, you get free parking at the zoo and 10% off).