Lice are a nightmare. My daughter came home from school with them a few months ago, and the whole family suffered for about a month. I never want to go through that again.
Things I learned:
The lice on a child's head are very easy to kill. We used the Walmart-brand lice shampoo (read the directions -- it's not just a matter of washing normally), and it was disgusting to see the little buggers washing down her back. Her head was bug-free in one shampoo. That part was easy.
You must re-do the chemical shampoo on Day 10 . . . and maybe another Day 10. I didn't like the "natural" shampoos.
The first hard thing is cleaning your house. My water bill was huge because I washed her sheets every day in hot water (and I set my machine for a double-rinse). I wasn't impressed with the mattress sprays, and I finally bought a plastic mattress and pillow cover. Then you have to clean the carpets, the stuffed animals, etc., etc., etc. Don't forget the car, her bookbag . . . everything.
Constantly deep-cleaning the house is exhausting, but if you miss just one louse, he'll jump back on the child's hair.
The second hard thing is getting rid of the nits, the eggs. They're clear/silver (hope you have a dark-haired child), and they're the size of a flake of dandruff. The hold onto hair tightly; you must slide them down the length of the hair to remove them. You can get rid of some of them with the little lice combs, but eventually you're going to have to move on to going through the kid's hair bit by bit by bit. I have a big craft lamp with a magnifying glass on a gooseneck, and I'd let the kids sit and watch TV while I went over their hair with a rat-tailed comb.
We did the olive-oil thing just about every day. It does make the nits/eggs slide off more easily.
Last comment: It's miserable going through this situation, but don't be too hard on yourself if you don't get rid of them immediately. My daughter's problem was discovered on a Friday, and I genuinely thought that if I did gave it my full-out attention all weekend, we'd be good to go on Monday. Nope. Not even close, and both my husband and I worked like dogs all weekend long on the problem. It lasted a month at my house. Several times we reached the point that we thought we were done, then the next day we'd find more.
I was amazed at how many of my friends had also been through this horrible situation, and ALL of them said it took them weeks to get rid of them. Several of them said they were "cured", then their kids picked them up again. While you're going through it, you can't have other kids visiting, nor can your kids go to other people's houses.
If you know that someone in the classroom has them, but your child doesn't yet, I'd suggest a long conversation about sharing hats, combs, etc. . . . and I'd suggest having your child wear a bandana over her hair to school every day -- it might help a little. The hairspray sounds pretty good too.