For the majority of high school, I worked at various barns - never got paid, just worked there because I was horse-crazy, my parents refused to buy me a horse, and I wanted more time at the barn. I’m not that old (24) so this was back in the mid-2000s, but I never signed anything or had any formal agreements - it was just a part of the riding world to me that nothing was ever really ‘nailed down’ and my parents were fine with that as long as what I was doing was reasonable.
However, with how things are now… I would look into any legal protection you might be able to get just in case.
I do see clanter’s point with the internship program idea but that never would have flown with my parents and I was so desperate for any horse contact, I was willing to just muck stalls all day and do any type of labor to be around horses. So while the internship idea is smart, you may cut out some great students who are hard-workers but can’t afford to “pay to play” and are willing to work to play.
But I can’t tell you how much I appreciated being given any opportunity to work, in any capacity, in a barn - I gained so much practical horse management and horse care knowledge, along with training knowledge, I really don’t know where else or how else I would have learned everything. Definitely protect yourself but seriously, I applaud you and those barns who gave me opportunities for opening up to hard-working kids who want to learn.