I'm buried in meetings today, so more posts will be coming later, but I just wanted to post a quick link for people looking to blast WiFi cheaply through those fortress-like walls of public schools.
Freeantennas.com offers DIY methods for boosting WiFi signal and the following video offers a few more details
Have your students give this a shot and report back. How does it work? I'll happily post any student reports. Happy hacking!