rehctub, there are simple standards for school zones. As an example those for WA: https://www.mainroads.wa.gov.au/BuildingRoads/StandardsTechnical/RoadandTrafficEngineering/TrafficManagement/SpeedZones/Pages/Part_C__Technical_Guidelines___Speed_Zoning.aspx#TOCh610

While improvements are possible, then need to be made carefully, as they are expensive to make and the consequences of a mistake can be high. As an example of the issues, see the NRMA's 2011 submission on school zones: http://www.mynrma.com.au/media/NRMA_Staysafe_School_Zones_Submission.pdf

So then there is the other issue, that being duty of care if authorities and a possible grey area they have created.

I say this because once booked in a zone without warning lights, one could ague that the authorities have marked some, but not others and, the fact that they have marked some,( not all zones with lights have schools/activity on both sides of the road) points to the fact that they knew that a problem existed, so why didn't they mark the one where the offense occurred. I think they have a problem if challenged.