That's because of flawed design usually. Architects cook up these lovely stylish renderings that the school boards find inspiring (particularly since it isn't their cash), which often involve flat or complex roofs.
Fast forward to the post-construction era, and that inspiring building now has 10 inches of water or ice on the roof. Water being water, it eventually gets in, usually around flashing.
Fast forward to the post-construction era, and that inspiring building now has 10 inches of water or ice on the roof. Water being water, it eventually gets in, usually around flashing.