We often have a lice outbreak every year - it's not uncommon.
Where's your school nurse on this?? You do have a school nurse.
If you've got a student with lice, send them to the nurse. And
check on-line -I think each state has established procedures
for how a school nurse and the school are supposed to follow up.
If you don't have a school nurse...
If you do, go to the nurse and asked to be checked for lice.
Maybe somehow the nurse doesn't even know this is going on.