What I sometimes think of is the risk vs. reward calculus. Yes, there are risks, for example, a teen schooling and training young horse under the watchful eye of a competent trainer, but great knowledge rewards.
There’s a potential reward in a competent pro competing or even schooling an upper level eventing horse in bad weather, because that is the nature of the discipline. You can take mitigating steps (helmet, body protector cross-country, making sure the horse is properly shod) though you can’t eliminate risk.
There’s also a learning trajectory in risk calculation. If it’s your first time on a young horse or riding out in the open cross-country, choosing a windy day might not be the best idea, while with a more seasoned horse or rider, it’s less of a risk because they are more equipped to manage any issues.
I’m a weenie, amateur dressage rider with no real competitive goals, so my risk calculus is going to be different than a teenage eventer who does. But that doesn’t mean I can’t try to push myself through a reasonable comfort zone, nor does it mean that every crazy risk the teen might want to take (or be pushed to by a trainer) is worth it.
There is also a trust factor with the trainer. Is the trainer good at reading students and horses? Sometimes this is the hardest thing to assess as a new rider. There are trainers committed to having their experienced students take reasonable risks to learn valuable new skills. There are also trainers who use kids as crash test dummies and bully them to ride horses no one should be riding who isn’t an experienced trainer.
