Security lighting is controlled in a number of ways:
ambient light sensors which turn the lights on when it gets dark
sunset/sunrise timers which turn the lights on from dawn to dusk
Passive Infrared (PIR) type movement sensors
PIR sensors are by far the most efficient option (as lights may be on for one hour a day rather than 12 hours) and can lead to very significant cost savings. They can also be more secure and more likely to distract burglars if the school suddenly lights up following their movement. It is also better for wildlife as permanent overnight lighting deters wildlife, particularly bats and owls.
When trying to reduce your school’s running costs, it is worth reviewing your outside lighting. It can be something which is often forgotten about but has the potential for bigger savings because it can be on for longer than internal lighting.