High school can still be competitive and regional. I’m referring more to the leagues in college usually offered through the physical activities departments which are usually super casual and for fun, or very light competition, and often entirely within a single institution. It rarely rises above the level of “Your High School PE class” which usually plays traditionally segregated sports co-ed because of the low level.
Like, my university has a casual in-university doubles tennis league in the spring and while I guess someone could abuse it, everyone is playing at such a low level the biological differences aren’t really even meaningful because it’s mostly people who are at best vaguely not out of shape but still really bad form. You’d be more in danger of somebody who plays in league tennis coming in and stomping everyone to make themselves feel big (which is why people who play league tennis are banned from intramural).
Also, I feel like you guys are moving the problem a bit. A trans woman on HRT can never compete with cis men either in a competitive environment. You could propose a “trans league”, but at levels like high school, even arguably college, that’s effectively a no-compete statement because you’d need the school to have enough 1. trans women that 2. want to play one specific sport which is a real “stars align” situation.
I’m also not sure of the evidence here. There’s not super good science AFAICT, and naturally the news focuses on trans women who win, especially in a blowout. I see a lot of people asserting one way or anything “this is because they’re trans”, “muscle mass drops sufficiently after <X time>”, “but bones”, and so on, but little in the way of evidence besides anecdotally having seen a couple trans women compete in a specific competition. It’s entirely plausible that say, the bell curve of post-HRT (post-bottom surgery?) trans women slightly exceeds the bell curve of cis women at the tail but the means are very close, for instance. And it’s unclear what to do in that situation because, as mentioned, there are a lot of extreme deviations that can happen in women traditionally identified as cis too, such as Caster Semenya.
This is why I brought up the strength bracket solution as an analogy to weight class. It would also allow, say, intersex people, AFAB NB people on low-dose T, weaker men (until they train enough to get into men’s), and so on to compete as well. Again, not fully baked, but is a solution.