With the caveat of the best school is in my backyard, here are my thoughts:
I have a son that's a freshman at St. Thomas. He absolutely loves it. Its only been 2.5 months, so hard for me to really comment on anything, but so far I think its been great. There are about 15 boys from his St. Anne class in the freshman class, which is more than any other catholic middle school sent there. But there are boys from all over Houston and every suburb in his class, from both public and private schools.
I have a daughter that's a junior at IWA. To me, it's a fantastic school for her but I could see why it may not be a good fit for others. It is very small, which understandably some don't like. If you don't know anyone going in, I would guess its hard to fit into a group when there aren't a ton of girls. She was lucky, as about 7 other girls from her middle school class also went to IWA. I like the academic side of it, and with the small classes its easy to get extra help. While they have sports teams, athletics are really more of an afterthought for the school it seems.