I don't jump, and my youngest daughter (13) doesn't want to learn. However, suppose my daughter DID want to learn jumping next year? As a Dad, I would be willing for her to learn, but I wouldn't just say, "Let's put out some bales of hay and get started!" At a minimum, it would be, "Take lessons or don't even think about it!"
In March, I posted this thread about injuries (Helmets and injuries - some studies (LONG!)). The studies indicate jumping is much more dangerous than riding flats - apparently at least 10X more dangerous, and maybe much higher (40X). That doesn't mean I think jumping should be banned, or kids not allowed to jump.
But what are some good benchmarks that would help a parent know their kid might be ready to start learning? For some examples (and I have no idea if any of these are relevant):
Sit the trot/canter without stirrups?
Ride solid two point for XX minutes?
Post without stirrups?
Steady lower leg?
What sorts of things can you see when someone is riding flats that would indicate the person could start jumping without needless risk?
Also - what level of steadiness would you demand from a horse before you think the horse would be ready to start jumping, say, 18" / 24" / 30"? Or does that question even make sense?
What would you expect from an instructor?