i have the same problem!! but urm well mine has kind of been resolved by the solution that my horse doesn't respect the smaller jumps so he doesn't pick his feet up and just goes through them, but he jumps amazing xc and i am now showjumping him about 2'9 3ft and he looks at them and jumps them properly, so maybe u should try jumping bigger? what is he like xc? also if too much of your weight is on his forehand he will find it harder to lift and probably knock poles down with his front feet. I've had this problem for ages its a pain in the bum, but u need to find a reason why he is doing it. I was competing today and only got one pole down in 2'3 which is a bit too small for him but 1 pole is a record!! good luck!
Put a cross pole up with the centre at about 2'3" or bigger and jump it from walk - that will make your horse use it's shoulder and pick it's front legs up. Also the \/ poles and gridwork are good