Break fence jumping habit

Question
Thank you for your quick response.  It is a 6' fence and we did stop them from jumping for about a year, I guess we need to reinstall it.  Are they doing this because we have not properly trained them?  When they are caught in the act I call them by name and tell them to come.  Some times they will stop and look back but then proceed to do as they please.  Do we need obedience school or is there something I can easily do or reference material that could help?
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Followup To
Question -
I have a male and female approxitmly 4 to 5 years old both weighing in around 55 to 60 lbs. They are a mixed breed, vet says both have shepard in them. During the summer we take them to the woods to run 2 or 3 times a week and camping twice a month, but now with the shoter days they only get to run once maybe twice a week. They have a large backyard that they can go in and out as they please and at this time I am not working. Off and on in the last 2 years they have found ways to jump the fence to get out of the yard. The last 2 weeks they have been getting out 3 or 4 times a week. We have walked the fence have tried tracking them in the snow but have not figured out where they are jumping at. What can I do to stop this behavior? When they come home they know they have been bad, I have skolled them telling them they are bad dogs, I have gone 24 hours sending them to their beds when they try to make up. Just this week I told them how bad they were and they each got a swat on their rear-ends with the back of my hand and sent to their beds. I just don't know how to stop this behavior and do not want to break their spirit or make them afraid of me."

Answer -
How high is the fence?  Unless it is 6' high, it is possible they can jump it anywhere.  You might look around and see if there is anything close to the fence they could climb on and jump out.  If you can't find and fix something like that, you will have to make the fence harder to jump.  It may be difficult to make any higher.  Consider adding an electric fence either at the top, or inside a little ways keeping them from getting close enough to jump it.  No amount of punishment will stop it unless you catch them in the act.  Even then, they may still jump it when you aren't there.  

Be careful punishing them when they come back.  They may decide you are punishing them for coming back.  dogs just don't think like people do.  

Answer
There are some things I don't think anybody can teach some dogs.  I taught my one Lab not to dig holes in the yard by catching her in the act a couple of time and scolding her.  I seldom even mention it to the the people asking how to keep their dog from digging holes because sweethearts like her are few and far between.  It worked for me for that dog.  I haven't wasted my time trying  it with any others.  

Good obedience training makes any dog easier to live with.  The dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members
outrank the 4 legged ones.  You can learn to play the role of top dog by
reading some books or going to a good obedience class. A good obedience class
or book is about you being top dog, not about rewarding standard commands with
a treat. Start at http://www.dogsbestfriend.com/.  Even once you have firmly established yourself as top dogs, I am not sure the dogs won't jump the fence and run off despite you calling them.  

Every dog should be taught ''Come, treat!''.

With the dog at the end of the leash, call its name and "Come" in a firm
voice. If it comes, praise it lavishly and pet it. If it doesn't come, repeat
the
command and give the leash a light snap. Keep it up with firmer leash snaps
until the dog does come. Do not forget the praise.  Then switch to a longer
leash or rope, about 25'.  When it comes well on the longer leash, you should
be
able to go to
off leash in a fenced area, etc. Once the dog is doing well, introduce come,
treat. This is for emergencies only when the dog has gotten loose accidentally.
Use it routinely and you will have nothing to fall back on when your dog is
headed for a busy street. "Name, come treat!" is little different from the
regular "Name, come!", except the dog gets a great treat when it comes. We are talking
a hot dog, cheese, etc. much better than any treat you use routinely.

Relying on come to control most dogs loose outside is risky, and I do not
recommend it.  Dogs are individuals.  Some can be trained to come when you have
no way to enforce it, but some will never be completely reliable even for the
most experienced trainers.