Indeed, 15 or 25 mph (24 or 40 km/h) are the speed limits in school zones (when in effect) in CA, for reference. But depending on the general movement and density and category of pedestrians around the road it could be practically reckless to drive that fast (or slow).

If my experience driving through a school zone on my way to work is anything to go off of, I rarely see people actually respecting it. 17 mph would be a major improvement over what I'm used to seeing.