Electric Fences aren't useless. If you can come up with a strategy (like my friend did) they can be life savers. The thing is, play with at least 3 people so that it's guaranteed that someone will start on the M1 Garand side.
After you start the match, the people/person on the Gewehr side let all the zombies IN. This increases the chances for bonuses, hope for the x2 points. People on the Gewehr side, do not kill anyone in the courtyard unless they get in. Let the M1 Garand side get them, they need the points.
After a single person on the M1 Garand side gets 5500 points, they should head off to turn the power on and quickly. Everyone should sprint to the power room and buy a weapon from the mystery box until they get at least one good weapon. Now the object is to hold down the stairs and power room. Once everyone has enough points, they should all buy the three perks available (Quick Revive, Juggernog, and Speed Cola.) After everyone has that and a good weapon, it's time to rush over to get Double Tap.
Head back to the start area, and open the stairway for 1000 points, and buy Double Tap Root Beer. Also, make sure to pick up an MP40 from the wall, along with the bouncing betties. DO NOT OPEN ANY OTHER DOORS! Now the object is to hold down this area. You should be able to have an infinite amount of ammo for the MP40, and get a Max Ammo every once in a while for whatever other gun you have.
Have two people watch the stairs/wall, and one person watch stairs out on the balcony. If you ever get into any trouble, walk out onto the balcony, set off the electric barriers and wait in there to reload and do what you need to do.
I haven't been able to get passed 13 with this strategy, but that's because the third person we were with left halfway through, and we couldn't watch the stairs as effectively.
Give it a try, it should work. ^^ *feels like a nerd for writing so much*