But to add to that, say you had a "older" horse you wanted to start jumping, id initially start them over trot poles and cavallettis/straight bars up to 30cms and stay at that height until they are jumping it properly eg close to the poles with their legs not overjumping it and then go up to the next height until they do the same etc etc. Its important to make sure that they can negotiable lots of different stridings, spreads, doubles etc at a low height below you move up.
A LOT of people make the mistake of when their horse is over jumping due to its lack of ability to judge height they think it is just demonstrating fantastic ability so they take it up in heights and the end result is an overfaced horse who will stop jumping.
Hope this helps
