Head Lice - can a school insist that your child must be treated with chemicals before being allowed back in?

[Aero]

Wasn't sure where to put this really, so it's here!
Discovered HL in dd's hair this morning, so took her to bathroom and wet her hair, then conditioned it heavily and combed through with nit comb. Removed all live lice and as many eggs as I could see and will probably 'treat' her later today, but, school were very funny about her being 'treated' and saying she shouldn't be there unless she is 'treated'. As far as I'm concerned, I didn't have time to treat with chemical stuff as ds1 was going on a trip, so we couldn't be very late, although we were a little late because of the time taken to condition and thoroughly comb her hair.
But what I want to know, is whether or not they may insist on this form of treatment. They have accepted her, but only when I said I had treated her (not mentioning with what). I felt really upset at the time!

Thanks natts - am going to ask the HT tomorrow anyway. I really shouldn't have been made to feel I hadn't acted correctly this morning. Felt really angry about that. The TA should have known better than to be so condescending!!

Well, I've spoken to the head this morning and she said that I had indeed treated dd appropriately and with the most effective method of getting rid of head lice. I haven't said as much (cos I'm a wimp really), but imo, the TA should have known this and not needed to ask the head for permission for dd to stay in school. Even after she'd asked her, it was implied that she was right because the word 'treated' had been used! She spoke to me as if dd had the plague and insisted that she needed to be treated before being allowed into school, despite me telling her I'd 'treated' her with conditioner and wet combed all the live lice out so it couldn't be passed on! This really needs to be made known to parents instead of us all buying useless 'treatments' from the chemist which don't work anyway! (Feeling bad, I used the mousse on her last night and wet combed again. Repeated this morning and still found one live louse! Proof that the lotions and potions do not kill all the lice, removing them is much more effective and I will not be rail-roaded into using the chemical stuff again!!