So, I've started schooling Jetta over some jumps under saddle recently. She's doing great and we have been jumping about once a week over an approximately 18" cross rail about four-six times per session. I am continually impressed with how well Jetta has taken it in stride. I was interested in how I should progress for training her over jumps. Jetta is turned four in February this year and I started her under saddle at the beginning of June. I feel like we have the most basic skills down and we're ready to take it up a notch. I did a search about how high you should be jumping a young horse maximum and found that it was quite the debated topic. Many people say that you shouldn't jump until 5 or 6 when all of their bone plates are closed, not only in their knees, but also in their spine. This makes a lot of sense to me, but I think the general consensus that I found was that around 2'-2'6" jumped sparingly and done the right way is not too much for a four year old horse to handle.
I was planning on building up to 2'3" or 2'6" over the course of this month as Jetta finds the small cross rails we are doing so simple. I have free jumped her twice over some larger jumps and I think she seems to enjoy it as even when I asked her to stop and come into the middle of the arena, she trotted over the jump one last time before coming in. I don't want to cause future soundness issues in Jetta, so I want to go slow with her. I am not planning on jumping anything big or scary and I will only jump sparingly because I want both her soundness and confidence to remain intact. Jetta will be five in three months so I am thinking that my planned jumping work load shouldn't be too much for her to handle.
I was looking at shows that I could take Jetta to this year and I was surprised that very few shows have anything under 2'9" (as I am a beginner in the world of Hunter/Jumper Rated Shows) but did find classes for 4 and 5-year-olds that seemed really large. Hmm... Overall, though, what I got out of discussions is that you have to jump a horse correctly and don't do anything that is so big it scares your horse and try to jump sparingly so you save their joints.
Here are some articles and discussions on jumping a young horse:
Teaching the Young Horse to Jump
Horse Channel Jumping Tips