Seems to pick up on the construction ones if they put a different speed limit sign there. Which is also why it does the 15 for school zone. It just isn't programmed to see it's a school zone sign and adjust based on date/timeThe USA is pretty consistent when it comes to speed limits and they are rarely "adjustable."
There are obviously exceptions for school zones and similar temporary time based changes like construction zones.
I've always wondered why they are unable to adjust or at least issue a warning of some sort that one is approaching or driving through a school zone...at a minimum. I understand the difficulty of adding the coomplexity of a time based/day based setting, but at least give a pop up which I can ignore on the weekends or over the summer.