During the entire rest of the day, schools are locked down like fortresses - the only way I could hit a kid with my car by speeding would involve putting my car through the god damned wall of the building, and I don't think a speed camera is going to do a single thing to stop that. So, aside from the two short periods every morning and afternoon, school zones are bullshit speed limits (and some of them even hold during SUMMER and IN THE MIDDLE OF THE FUCKING NIGHT) designed to provide a quick and easy +20mph speeding fine with a multiplier of 2. Sometimes they'll slap a few cones up for a x4 school+construction multiplier. The natural evolution of this, of course, involves a speed camera to tirelessly enforce the 15mph speed limit (down from 40) at 2AM.