How high should a 12 year old jump?

I agree that age should not matter.

Training and ability should.

So if you are comfortable jumping that high, and your trainer thinks you are capable, then go for it!

I was barrel racing at break-neck speed well before the age of 12. But I dang near grew up on a horse, so I could handle it.

If you have to ask this question, either you're not ready to be jumping that high or are asking for bragging purposes.

In general, age should not matter, it is about experience. How regularly you ride, how long you've been riding for, etc.

Do you have photo/video proof of this? I'd love to see it. Otherwise, I can't see how a 12 year old would have the experience to jump 4' well. But if we are going to the bare bones of it, I could probably jump 4' when I was 12. But I would have caught my horse in the mouth, flew my legs back, got left behind, etc. over the jump. Just because you can make it over a jump, doesn't mean you can "jump 4'" It means you can survive while your horse throws you over a 4' obstacle.

Jumper, not true, really. Given the right horse and the right instructor I know many young riders who could jump 4ft well, that isn't to say they should do it without an instructor present. I am only cautious to tell OP 'that's fine' because we don't know that she DOES have the experience to do it well.

Ah, you are correct. I was just showing doubt, with what little information was given; it sounded like the trainer sort of just pointed and told her to go for it. But you're right, thank you for clarifying.