You jump your pony but he knocks poles loads?
If you are with a trainer, discuss this with him /her. The pony could be rushing the jumps and losing his sequence. You can work on regulating his pace so he has a steady rate of approach to the jump. Try some work over trotting poles. Then place a small jump at the end of these. Check that your approach is at the correct angle so that he can take off from a balanced position. Lay two rows of coloured rope or straw either side of the ideal approach lane. Do some work yourself in judging how you will approach a jump. Walk it out on the ground. Ask someone to video you, then watch and see if you can spot the problem. Take the video to an experienced friend or a helpful trainer and ask their opinion.