[In Twilight there is no explanation as to why school was not called off when the roads were completely unsafe. This is my attempt at an explanation.]
Teacher outside of the school:
"You're probably all wondering why school wasn't canceled when it obviously should have been. It was an accident. When Margie went- sorry, when Ms. Stevenson went outside today she slipped on the ice and took a hard fall. She's recovering in the hospital now and we're told she's going to be all right... eventually, but when she should have been announcing that school was canceled she was incapacitated on the ground.
"Everyone else who might have cancelled school just assumed it had already been done. They didn't find out it wasn't canceled until people started showing up and wondering where they were.
"None of us should be here today, and we won't be having any classes." [sounds of jubilation] "But we can't let you leave yet." [many sounds of unhappiness] "Not until the roads are safe. You were all lucky to make it this far unharmed. Getting back on the road goes beyond tempting fate." [grumbling]
"We've got hot chocolate being heated up in the cafeteria, we're breaking out cards and chessboards, and we're trying to figure out how to get Netflix on demand hooked up to one of the projectors at which point we can vote on a movie. The computers are all yours if any of you want to go on facebook to tell everyone about the evil teachers who are keeping you at a school with no classes.
"This situation sucks" [eye rolling, a few giggles] "but we're trying to make it as painless as possible."