Hi there,
We've just finished doing the same at our local school - keeping chickens at school is becoming very popular these days...
Yes, a 1M electric fence would work - but I wouldn't go down this route unless you can be sure none of the children will touch it or fall onto it. It won't kill them but would probably give them a fear of chicken runs for the rest of their lives!
A fox will usually sniff first and when he touches it he gets a shock and the fence then becomes a psycological barrier in the future. To jump over it, he would put his paws up against it and again get a shock. Before digging he would try pushing the fence or climbing.
You also need to stop anything touching an electric fence (like long grass) or it will short out and not work.
6 foot is usually about the height people go for. If you can fence the top of the run too - then even better. You'll need a good 8 to 12" in the ground. I turn it outwards too so it's even harder for Mr. Fox. I have seen two foot turned outwards on the surface - pegged down to the grass, then, believe it or not, with the action of earthworms, this will slowly dissappear beneath the surface of the grass.
Foxes can actually grip the 1" chicken / rabbit wire and tear it apart with their teeth but this has only happened to me when I lived in Wales during a very hard winter with snow on the ground and very little food around.
The best defence is locking the chickens up at night in their house.
If you can afford it, I swear by these
automatic pop hole openers
One final idea, to raise money, this school created a small 'free range egg business' :
keeping chickens at school article.
Good luck and let us know how you get on!
Tim