Originally Posted by whisp
My horse does that too, but only if the jump is under 2ft. My instructor told me that it could possibly be boredom - why should he put the effort in over small jumps? Rather save the energy for the higher
I couldn't disagree more. He's ducking out because he knows he can. And your not properly correcting him.
Constant leg pressure to the jump, and opening the opposite rein to which he likes to run out. (Almost all horses have a preferable side they like to run out. I bet you he does too)
He's just being a jerk. Don't let him get away with it. And absolutely do not give up on that jump. If he runs out, do the same jump 5 more times. He'll learn running out = more work.
Jumping him too high too often is a risk to his health. Save your horse and save the big jumps for the ring or lessons.
Hope this helps.