L.
We went through this this past summer, and the doctor prescribed some stuff that did not work.
Here's what did work: Buy a bottle of olive oil and coat the hair and scalp with it, cover with a plastic bag, shower cap or something and leave it on overnight. In the morning, use a nit comb while the oil is still on the hair. You have to do a section about two inches at a time. It is very messy, so don't do it over carpeting.
Next, put a shampoo for oily hair on the hair , then wash and rinse it. A blow dryer is good because they don't like dry heat.
Nit comb the hair every day for a week and if there are still nits, repeat the oil treatment. It is non toxic and relatively cheap.
I bought some shampoo, and conditioner and repellant hairspray to use once I knew they were gone to prevent her from getting any more from school. I got them from Fairy Tales hair care. You'd have to google them.
Good luck
L.