Are snow covered sidewalks a safety hazard that would call for school to be cancelled?

So I live in Maryland and we got a lotttt of snow yesterday. I'm trying to predict whether or not we will have school tomorrow and I was wondering if school could be called off if sidewalks are not plowed around neighborhoods. I've heard that before. And it's not like kids can just stand in the street waiting for their buses right? There is about four feet of snow on the sidewalks around town fyi.