As for the study hall thing... I can't speak for that. I teach elementary school, so I wouldn't be able to leave a full-day study hall. I do remember when I subbed for high school teachers, it wasn't unusual to be left with "study hall," especially if it was a Monday or a Friday. I'd agree that four teachers just leaving study hall kind of stinks... I get not wanting to leave something new for a sub, but I'd think some type of review activity would be better.