If its a youngster then lots of grids, poles on the ground etc to keep them thinking and working out where their legs are.
With an older established horse I would want an instructor to watch me to determine why the horse is rushing, as there are lots of reasons and lots of solutions
He is 12 but very green and hasn't done much at all. He is only 14.2 but has the scope and we have done around 90cm so far. We do have lessons but can't afford them too often and often have flatwork lessons. He is quite quirky and not straightforward.
Just wanted some idea of polework or small jumps to make him think a bit more.
Obviously the best idea is to get your instructor to take a look and help you both together.
One of my boys is an absolute tank for flatwork - jumping? Prepare to take off round the ring. He's strong and he's fast, but the problem is that allow he is fast all of the time (which we are trying to work on) you can feel him rush to the jump. Spoke to my instructor and she suggested trying to take the run up away. So with small jumps we started trotting around the space quietly, really trying to keep our pace slow and calm (for us) and trotted down towards the jump, did a trot walk trot transition just before we turned towards the jump, and then turned him with only a couple of strides left. This was repeated what felt like 100 times before he actually settled and stopped rushing. It's a very boring exercise, but our instructor identified a possible solution for us and it was definitely a very big step in the right direction.
Lots of poles!
If he only sees pole when you jump that could be why. Also if you have jumps always in the same place they will anticipate and and zoom along!
Where poss have a lesson and get some eyes on the ground to asses for you
One really useful one is to ride a figure of eight with the centre cross in front of the jump - desensitises him to seeing the jump but not being asked to jump it. And no, it won't teach him to refuse, but to wait for instruction. Start at walk and build to trot and every now and again pop the jump, then immediately go back to your figure of eight. The jump then just becomes part of the pattern, rather than something to anticipate and get excited about.
Could you maybe try and jump him on a lunge line over some cross poles etc and gradually get higher? Sometimes if he has been jumped in the past, if previous owners have socked him in the mouth on a landing they can be anticipating pain which is why they zoom over it. So by getting him to calm down jumping it on his own with no tack etc, he may relax a little and slow down enough for you to help him relax when ridden. Just a thought
My little mare rushes, the only thing that stopped her charging the last few strides was doing a walk transition before the jump, walking into the, then kicking like anything for the last stride- put all the energy in the right place for her to jump progressed to just a short bit of walk, then just a bit of trot... She's by no mean calm to jump but she has a rhythm now and doesn't run through your hand x figured it was a lack of strength that caused it, the moment she felt better on the flat, her jump improved tenfold xx
My instructor suggested that I trot 10/15m circles in front of a fence until the horse stopped anticipated that she was going to jump. When she either stopped rushing to the fence or started to anticipate the circle, she was asked to jump. Another exercise she recommended was to either walk to the jump and ask for trot/canter a few strides before the fence or to actually halt about three canter strides in front of the fence, then ask for a halt to canter transition when the horse stood patiently. Both worked wonders as they taught her that she had to wait until she was told to go over the fence and not assume that was what she doing, (though the latter may be better for when he's more experienced)