When building a new school the info view activates when the school is selected in the build menu. The info view shows the current availability of school services as well as the coverage of existing schools of the type selected. In the info view the roads are green if there is coverage , if the roads are gray there is no coverage available in that area.
Using the info view from the menu will highlight residential structures in grey-ish purple if there are citizens not yet educated to the level selected living there.