what I can use to kill head lice with one treatment

I have 3 girls, so needless to say every year when school would start they would come home with head lice within a week. My mother told me to use a shampoo and condition that has coconut as the fragrance. I have used Suave coconut shampoo and condition on them for 2 years now and they have not had head lice at all.
I also have a friend that does the same thing with her kids and it has worked for them. Guess the lice don’t like the smell…don’t know just know it works!

tea trea oil mixed with shampoo usually few day eucaluptus oil straight to the hair and scalp leave on 30 minutes .shampoo out 3-4 times still not gonna get the eucalyptus smell out but most and its not a bad smell.alternate 1 day tea tree one day eucalyptus for 2 weeks.all lice should be gone providing u wash all ur pilow cases and bed sheets i would suggest daily if too much for you then at least 3 times a week and vacuum everywhere at least once or twice a week or pointless get used to critters eating your scalp.