my mare is 5 and I have only sone a few jumps up to 2;3" in her entire life time and that was only a few months ago, at three there knees and legs are not fully developed and they are mentally not ready either, i have not pushed my mare 2 hard, she has only been ridden on the flat from the time i broke her by myself until now, and she is 5 and a half, her flat work is amazing because that is all i ahve worked on, she has done a few jumps but deffinately not many