RE: does anyone fly in school gyms??
Adoman-
Are you an AMA member? That takes all the "liability" sting out of the issue. If you're flying according to AMA safety rules, you're covered, inside or out. That actually makes it EASIER, in many cases, to secure a site. And don't worry- you can keep quiet on liability, but it will be the first thing any site owner will ask about!
As iflyj3 said, a lot depends on the contact. Around here, the individual school's janitor has the final say, because the principal, generally, just ain't gonna come out on a weekend or late at night to open/lock up; it's the janitor. We were lucky enough to have a member of our group (Lexington Model Airplane Club) who knows the janitor at the new big site personally, and knows her well enough that she gave us a discount- we're getting the "non-profit group" rate! And don't be afraid to ask around- we got a HUGE site, because the janitor at a smaller school (with a smaller gym), that we looked at first, suggested the bigger school to us.
Tip: You might want to stress the fact that there's no setup or teardown involved, and what you're doing won't make a mess. If all the person has to do is unlock the doors, then turn off the lights and lock up afterwards, they'll be more receptive to your asking to use a site.
Steve