I have two 1 yr old Labradors that keep jumping to my neighbors backyard. I installed a fence on top of the wall and now they're jumping to the next door backyard. I can't find any training exercises to teach them not to do it.
My pup and I would pass by a home where an English Springer Spaniel lived when we would go for our walks. The ESS would jump over his fence and walk with us as we went. When more agressive neighborhood dogs would approach, the ESS would do circles around us to protect us, and then jump back into his yard when we passed his home again.
Jumping fences just seems like a way to break up the day, but there are three possible solutions.
You can build up the entire fence so that he isn't able to continue jumping it. This is not going to teach him anything. He is still going to look for ways to get out of the yard and explore.
You can put an invisible fence around the inner perimeter to teach him to stay a foot or two away from the fence (thus hindering the jumps). You could actually do the back and front yard and give him access to the backyard when you are out and both yards when you are home. I have seen many a dog who are completely content inside an invisible fence.
You can keep an eye out and use a very firm, "NO!" when you see him in action. This is what I do anytime my dog(s) are doing something I want them to stop doing. You really do have to catch them in the act, but it works. My lab, Zelda, was forever digging under the fence to roam. Saw her digging under it one day, opened the kitchen door, "NO!". She never did it again (whether I was home or not).