alt Hacker NewsThis link claims this is for highways. Does TxDOT have a wider criteria for "highway" than the standard FHWA criteria? Under FHWA I would presume that school roads would be found on local or collector roads, not highways, but I'm not familiar with the streets mix nor the grant landscape of Texas cities.
Yes, there are different criteria for different roads. Presence of schools is one of them. In my neighborhood, the speed limit drops to 25 mph through school zones (it's 40-45 mph outside of the school zone).