I have three german shepherds and one of them jumps my 6ft fence weekly. I just got a call from my neighbor at 6am yesterday, telling me my puppy had jumped the fence. the best way is try to correct them off of it. my dog would climb a 4ft fence, then jump on some bikes that i had leaning on the fence. it make him easy to climb it. my other two shepherds are largly, so no chance in them jumping the fence. i have methods that work for me, but most would probably disagree with it. what i did with other bad behaviors, is make him do it when im watching and use verbal commands to make him not do it. usually it works, but sometimes, physical corections are used.
i would try lettace panel first or use some type of metal fencing. shepherds hate putting their feet in metal fence. i did it to the other side of my yard, and they dont jump it.