Rosemary or lavender oil, one drop behind ears & back of the neck. They don't like the smell of either and my friend used it all through school & only got nits once 🥲
Hedrin have a spray you can use x
We used tea tree oil as kids, my dad mixed it with our shampoo and I think we only ever had nits in the house once.
Hair spray makes a barrier. But obviously if heads are touching nothing might prevent. X
My mum used to comb my hair with a nit comb after school every day
I’m not sure there is anything you can do apart from hair up/not go!!