(this is a revised post from last year)
Supposedly, kids pick up lice at sleepaway camp and then it gets spread at schools. Sometimes, it's not announced by the schools when there is an outbreak. And when your child does get head lice it is a MAJOR production to get rid of it because of the way lice lay eggs (they take 7-10 days to hatch). So, you can eliminate the lice but still have recurring outbreaks.
Many of the products you find at drug stores also can be too weak to really kill the nits (eggs). Or some of them use harmful chemicals to kill them.
Considering the expense and hassle of dealing with lice you can work on prevention by dropping rosemary oil into your child's shampoo. Also, lice love clean hair, so consider putting some mouse in his/her hair to coat the hair.
If you buy or borrow used hats, clothing, sports uniforms, hair pins, stuffed animals or bedding then be sure to wash in hot water beforehand. Combs or hair pins should be soaked in Lysol or rubbing alcohol for an hour.
A site I highly recommend is Fairy Tales Hair Care for Children. They carry all natural, organic hair products. They carry a Rosemary Repel Shampoo ($21.95) and a Leave-In Conditioning Spray ($9.95). Link here. Also sold locally at Pumpkin and Bean kids hair salon and Englewood Beauty supply (both in Englewood, NJ). I also heard that you can buy the Rosemary oil at Whole Foods and drop that into your kids shampoo.
Next year, if you send your kids away to camp then consider including these in their toiletry bag. And also at the start of the school year, be sure to use these preventative measures.