Not sure what it was, but it was apart of a series. I don’t remember how many were in the series. It revolved around a specific classroom in a HUGE school. I don’t know why, but something in my mind thinks this school was really tall. Each book had stories that revolved around the students. Two things stick out about the series.
One of the children could only read upside down. They worked forever to try and get him to read rightside up, but I think in the end they resorted to a headstand to fix the problem.
The other thing is this. At one point a substitute was called in. She was a mean old hag, I believe, and she wouldn’t let the kids look in the closet. At one point, I think it turns out she was a rat. Or something to that effect.
I’m 19 now and I read it when I was about 7 or 8. I know these hints might not be enough, but I’m hoping someone out there has read this/these books…