I'm a teacher as well, and have lost 2 snakes due to improperly closed cages (either myself or a student). My science classroom is connected with 3 other classrooms, and a huge lab storage room, so a search is near impossible. Only advice I can give you is that if there is no way it can escape your building, it WILL turn up, whether in your classroom or another teacher's. I lost my ball python for 2 months before another teacher came running and screaming to me that there was a huge snake in one of her drawers. I also lost a rosy boa for nearly a year, before another teacher came running to me freaked out about a snake she found in her classroom.

Just let everyone know that you lost your snake, and besides some frazzled nerves, it'll turn up eventually.