I had the same problem with Max (rott/shepherd).

We solved the problem by putting a dog run inside the fenced-in area. There are two posts in the ground, with a cable between them and a chain hooked to the cable. He can run back and forth between the posts. You have to be VERY, VERY careful not to make his line long enough that he can still jump the fence while he's attached to the run. Otherwise he could strangle himself, KWIM?

We have changed our lifestyles a lot in order to not allow Max out! We have to keep all windows shut enough that nothing more than his head will fit out, otherwise he breaks the screens out and jumps through!

Our screendoors are the type that he can't get through, and we keep them latched at all times.

We sat down with all the kids and talked to them about the risk of him getting hit by a car if he got out of the house. So they're all very good about checking to see where he is before they open a door. When we're coming in the house we open the door a little and stick our heads in to see where he is before we open it all the way.

I also take him to a place where he can run offleash as often as possible. There's nothing in the world that this dog loves more than running - that's why he tries to get loose! Do you have a dog park?