They don’t want cars near the school when kids are coming in or when they leave. That sounds like a sane approach to me…

The idea is well-intentioned, but implementing it by making drivers try to parse arbitrarily complex conditionals while driving is unwise.

There's a sign near my house for a school zone with a reduced speed limit, that used to have conditions similar to the GP's example (though not quite as bad) But they recently attached a yellow light to the top of the sign and changed the condition to "when flashing." That's a much more effective solution.