I would so laugh if it turns out one of the schools neighbouring houses has an open wireless unit and the school laptops are jumping on to that and you have just changed the password on it.
heh, i got into the admin console with some other standard password. Changed the admin password and messed up the settings up(disabled dhcp etc) (I know, I'm evil ;-) ) so now the laptops are connecting fine.
He can always hard reset the thing, but since it was standard password protected, i don't think he knows a lot about these kind of things...
When the problem occurs again, i'll have a lookout for some rogue AP's in the building with my smartphone.