If Im being honest I think that you can teach basically anyone to stunt with proper technique, drills, and skill progressions. I tend to look more for athletic ability, tumbling/jumps, body awareness, grades, and dedication - but I think it's probably different for every school.
My school has a history of eligibility problems and kids not taking it seriously, so my main focus is using tryouts to find girls/boys who are hard workers and have drive. I do a lot of conditioning and drills and other things that are repetitive, tiring, and not the most fun in the world to do.
If the kid sticks with it through/takes seriously all of the exercises, motion tech, drills, and frustratingly basic stunts (sponge, prep, back down. Over and over), then I can trust that when we get to working drills for harder stunts, or when competition season gets rough, that they won't bail on me or give up. I write down any time I see and eye roll, a side eye to a friend, or someone half a$$ing what they're working.
I also spot some each day (no swing back handsprings only) and work with tumbling basics. I'm not expecting people to get a handspring, but ideally everyone would have a decent roundoff or cartwheel step together. When I spot I give them 1 small thing to try to fix on the first handspring, and then spot them 2-3 more times. I'm looking to see if they can take direction and attempt to apply it to their tumbling more than I'm looking for natural tumbling talent. There are some kids that get upside down and lose all awareness of their body, and long term they are a lot more work to get to tumble. If the kid can focus enough/be aware enough of what their body is doing to change something small in the first practice, then they will be much easier to train to tumble.
If they can do a good cartwheel step together and/or roundoff, and if they can take direction starting on day one with no swing back handsprings, there's a good chance they can get a back handspring in a season with enough work and drills.
Then I look at their grades ;)
After all of that I have a pretty good feel for the talent pool and I start making stunt groups that I think would work well together, then pull in lower scoring kids who were in the "maybe" pile skill wise but who were focused/disciplined/happened to be the right size and not stand out in any negative way to fill in the holes in groups.
