My aunt's once and for all method. Vaseline.
My sister and I used to get lice all the time from school, got sent home on a few occasions too. Well my aunt heard on the news about using vaseline on the head. The one minor problem, was she didn't remember how to get it out. After about 2-3 days of greasy hair, pulled back into a ponytail/braid to try to make it less obvious, we found that simple green works. And simple green is a non-chemical degreaser (or something like that, it's less harsh than others). My aunt and I both had greasy hair, she didn't want to take any chances of getting them. But I never did get them again after that, and that was May 1997. I also remember it vividly because my aunt chopped my hair off to my shoulders and I was very bitter at her, and I have yet to cut my hair that much ever since.
The key to getting rid of them, is cleaning towels and bed linens in hot water. For furniture and flooring you can use a flea powder/spray (Adams I feel is best). Lice, fleas, roaches, they all fall under the same category. Don't forget the back packs, brushes, and anything else kids put their hair near to.
Rids and all the other shampoos are waste of money. They might kill off some, but they don't do much after the second go around. I think it's the fact of life, especially when kids are in school, as nasty as those little buggers are.