http://www.chiefdelphi.com/forums/sh...ti+school+team
That thread had a bit of information regarding teams with multiple schools, and probably contains a few excellent resources you can contact.
Our team had people from other schools before starting teams at those schools, but there is always flexibility in that sense. Obviously, insurance is an issue, but you may want to come up with some kind of team policy that protects members regardless of whether they attend the same school.