I went to a charter high school that used several old elementary school buildings within walking distance of one another. We had bells, but they weren't used. Instead, teachers would walk around announcing loudly that it was class time, first in the morning, and then after lunch. No tones, no PA system.
One time, some joker decided to activate the bell. All the kids in the building were PISSED.
_________________
"I'm sorry, I seem to have a tin ear for other people's feelings..." -Naoto Shirogane