I have figured out the revenue enforcement part of it but I think turn about is fair play so advocating for more safety which would decrease revenue because people would be less likely to be caught off guard (it is about safety) with the same flashing yellow signs showing the school speed limit in the center would put these cities in no win situation.

How can they argue against more effective school safety?

I mean from their point of view if a child is hit but the drivers pays the $50 fine for speeding they have done all they can prior to the incident. Obviously post such an incident the driver has consequences but this is about prevention.