I drive past two schools, once a week at about 8.30am. Both schools have lots of people and cars around them; both have 40km/h flashing electronic signs operating; both have dedicated crossing places, one is a kea crossing, the other has a zebra crossing; and both have trained children and adults monitoring and operating these crossing places. They are well managed school speed zones.
These are busy and congested roading environments with significant numbers of boisterous, but potentially distracted, vulnerable young people on their way to school. You become naturally cautious as a driver, but it can be quite challenging to reduce speed to 40km/h unless the reason is patently obvious.
There's a lot going on around schools these days which is not limited to the classroom. In a traffic sense, schools are concerned about congestion around their entrances and their drop-off zones. Many would prefer their students walked or biked to school but don't know how to effect this. They worry about the speed of vehicles around the school and how children can safely cross the road. These issues are all part of the school staff responsibility before the real work of education can begin.
When I was a kid we walked, cycled or bussed to school. Parents rarely dropped their children off on the way to work. But as urban schools increase their roll numbers with little increase in physical area, the challenge of traffic around the school increases and each school has its unique set of issues.