This is my first post on this website, so help me out if I'm doing anything wrong, posting this in the wrong place, etc.!
I have three TB's that I ride all the time, and I am training my newest one to jump (I have trained TB's to jump before, FYI). I started with lunging her over ground poles, which she did really well with... then we tried a little crossrail, which she just trotted over instead of jumping, but did it well. After a few sessions of doing this, I tried making the crossrail into a small vertical (about 1' 6", she's 16.2 hands and she could step over it if she wanted). Every time she goes over it, she knocks it down. She doesn't seem to care, or be trying any harder. She does jump it, but usally knocks it with her hind legs, and sometimes with her front ones.
I have the almost the same problem with a different TB of mine, but he's already past the groundwork of jumping (ground poles, lunging over jumps- I've free-lunged him over 4' jumps) but when I'm on him, he always knocks poles. He even knocks cavaletti when I try to jump him over them, and they're TINY!
Please help, I have no idea how to fix this! Well I have a couple ideas, like trying to jump them over solid jumps, but that could be very dangerous.... help!!!