I was a kid but I do know the clocks in my elementary, middle, and high school were accurate. Near end of day, we would impatiently stare at the clock waiting for the release bell. Being a public school, the clocks were bolted securely to the wall. Being little shits, students would probably steal them if they could, LOL. So how did they keep 100s of clocks on time? I asked and was told by the school maintenance that it was done through power.