I often cut them off for shorts if they still fit everywhere else. I have patched jeans from the inside. I put the patch inside the leg and use Wonder Under around the edge. When I iron it on it holds well. Then I trim the fringed edges off and try to make it look as nice as possible. If they are too short then I send the pants to my sister and she adds decorations to the bottom. She has also sewn appliques on or buttons and stuff. I'll add a link to her etsy site, not to try and sell you anything, just to give you an idea about what to do to extend their life, to inspire your imagination.
BUT, these are no longer school clothes. I think kids are cruel and I try to have the kids wear their better clothes to school then change into play clothes when they get home. To me it's like their job, it's their job to go to school and get an education, it's my job to provide a home for them. If I work then I dress for the job, they dress for the "job" too.
These jean skirts were purchsed at thrift stores and rehabbed...or embellished, whatever you want to call it. But look how cute they are, any hoes that were there are gone now and the item looks designer good.
http://www.etsy.com/shop/dancingdragonfly?section_id=6568073
I hope you are inspired to create some awesome looking repairs.