If you're interesting in tumbling and stunting, get going in cheerleading. You have two years of high school left right? There can be some pretty sweet deals out there for good male cheerleaders in college - there's a lot of coed stunting spots the bigger teams need to fill. Plus guys just do mostly tumbling and lifting, it's not going to be like dancing or anything if you're worried about that. You could look into going to open gym at a nearby gymnastics (or all star cheer) gym, or take a tumbling class. If you don't have mens' gymnastics at your high school (which most places don't) then consider cheerleading if your school has it. There will likely be instruction that is free or at a very reduced fee for being part of a school team. And if any other guys give you trouble about it, well let's just look at the situation

They're just jealous.
Edit: also, a lot of school teams work out in the summer going to clinics and group classes and stuff. I just got done working exactly that tonight. So if your school has it and you want to learn, you should contact someone on the team and ask if they are doing any tumbling and stunting classes you can join in on.