I wholeheartedly agree with aussienic, Vinegar is the best thing ever!!!

I come from a family of five girls with incredibly long and super thick hair, and being in school, you get nits all the time.

While conditioner does work, it's not as good as vinegar.
Vinegar breaks down that superglue like stuff that nits excrete to bind the egg to the hair. It dissolves the glue, and the eggs just come out. Usually even if you miss some, the glue has broken down so much that next time they wash their hair, the eggs will just fall out and go down the drain.

And you need a good brand new comb to get the actual nits out.
Just do the vinegar wash, comb through, leave the vinegar for an hour or so, and then wash out with shampoo and conditioner like normal and your kids hair will be beautiful.

Do a comb every day for a week or so and the nits will be gone.

And even if your kids don't have nits at the time, a comb through dry hair once a week will help stop the lice coming back.

It's been working for us girls for the last 15 years of schooling.