- indicate whether you understand what's being going on in the lesson
- see how near your target grade you are
- take part in quizzes ("hold up green for A, yellow for B...")
- cross the road
Why? Are parents and their children so dim that they can't understand percentages, so must have "bad" numbers thrown at them in colours? And where does this leave the colour blind? You'll have to actually say "that's red" or whatever.
The idea of traffic lights seems to be so popular with Temple Moor that, no doubt, in years to come, Temple Moor will be using traffic light systems for positive discipline, the healthiness of school meals, your uniform and probably even your health (because regular attendance to the HYPS clinic will be compulsory).