I had the same problem, when my son started school nits came home, and my 2 1/2 yo daughter caught them.   I didn't want to put chemicals on her, or the boys heads so I asked my mum.

She said when she was young every child had their hair oiled once a week, and nobody ever had nits.   I tried this, and still do with my children.   I have also tried conditioners etc, they do work to some extent, but none are as thick as the oil so they aren't as effective, also the oil doesn't cost as much.

Coat the hair thoroughly with whatever kitchen oil you have in the house.   It's much thicker than conditioner and the nits don't stand a chance as they suffocate.   Comb the oil through, wrap in a towel, just so the oil doesn't get on everything, and wash out 1-2 hours later.  Sometimes I leave it in overnight.

Repeat every 7 days for 2-3 weeks to catch all the eggs that hatch in between.  (or better yet, just make it a habit for every sunday night etc).  It's interesting to note that with all our technology today we still haven't found a way to penetrate an insect egg to kill the blighters before they hatch.   Wash all the pillowcases and sheets etc, and put the pillow and matress out in the sun for a few hours as the nits don't like sunlight.

The benefit of this is that the hair becomes wonderfully thick and lustrous with the oil treatments, and you haven't spent a fortune on expensive products, or put chemicals on your childrens heads.

And in all these years I haven't found a conditioner or a chemical that works as effectively or as quickly as good old kitchen oil. 

Thanks for sharing worth a try!

i was told from my kids teacher that if you buy cheap conditoner and leave it in over night