No once a week for 3 weeks should do it, but depending on the infestation and to get the eggs out you should use conditioner on dry hair let sit for a couple of minutes and then comb through with the lice comb atleast every 2nd to 3rd day at bath/shower time, just makes it easier to get rid of them. I would do the three weekly treatments though even if you think you have everything out, they are good at hiding and holding on to the hair so definitely follow through on the entire cycle. Did you let the school know? They will send a note home for other parents to treat their child's hair, it is anonymous so no one will know who reported it. There is a recipe somewhere on the net here but basically,it is 250 mls of water and about 5 drops of eucalyptus oil and 3 drops of tea tree oil and 3 drops of lavender oil. Or you can add a about 10 drops of each to a cheap conditioner. I think it works!! And it smells nice.