I agree fully... Despite the fact that one of my previous comments might have sounded too positive, I must say that reading your comment has just brought back so many bad memories. I'm so greatful that my last school was perfect: especially the fact that I had 26 hours a week, but given that they were junior 1 and senior 1, I only had 2 lesson plans to submit per week. That made the whole difference in the world.
Preparation time is never considered by the company. That is a real problem. I remember being in a kindergarten and - due to summer schedules - having 3 classes in the morning, and the 3 same classes in the afternoon!!! Do the math: that's 6 different lesson plans A DAY or 30 A WEEK. Eventhough I only submitted 3 a week to the company, it was tough planning due to the fact that you just have to be ready with young children... There's very little room for improvisation. I still wonder how I did it.
As I said it in my other post: read the contract carefully and sign knowing what to expect. There are many surprises and if you think or analyse what's happening to you too much, you might just be heading towards a burn-out. For me, it was Carpe Diem... One day after another.