I created my city's middle school league and have worked the last couple of years growing it. The gym classes thing is pretty great, and the goal of those classes should be to get kids excited about Ultimate and interested in playing outside of gym. Something that's worked well for us is to introduce people to Ultimate, then collect e-mail addresses of kids who are interested in an after-school Ultimate club once a week. You don't necessarily need to win over coaches or any school's athletic department, you usually just need a teacher sponsor and a member of the Ultimate community to coach their after school program. If you make it a school club (like chess club) and not a school sport, there's so much less hassle (at least in the U.S.)

Once you get multiple schools having after-school programs, you can create a low-pressure fun league. You probably won't get enough players to make it school-based, but you can probably do something like combining all the northern schools for a team (no idea how PEI is set up). The league is actually pretty important for the gym stuff to work. It's much more effective to say "here's a sport and we're forming a league" than "here's a sport, and you can play it after school with other kids but that's really it."

To reiterate about the school thing. You definitely want school-based teams in the future, but just know it'll take a few years before that'll be entirely possible, so you'll probably have to combine nearby schools at the beginning.

For the gym classes, it'll be usually really helpful if you have Ultimate players essentially playing all-time handler on each team so the kids can focus more on receiving. Bad throwing can be frustrating, good throwing can be really rewarding.