I really hope you find your snake in good condition.
I hate to be "that" guy but I gotta ask. What on earth were you doing with a snake in a class room in an enclosure that doesn't have a keyed lock??? That is just asking for trouble.
Do the other teachers know he's loose? How about the parents? I know and you know that the chances of a student getting hurt by this snake are extremely small but I highly doubt that every parent will know that and some will be pretty upset. It's just irresponsible on so many levels. You have risked the safety of the snake, the sanity of the parents, and possibly added more bad press for us all.
What happens if a child is bitten? I know that's a million to one chance but there's still a chance. The snake could find a home in a desk, in or under a book bag or jackets. If the snake is stressed, which it probably is, it could easily strike if startled. If that happens I'll probably find out by watching any news network.
Sorry to be negative but I feel like it just had to be said.