From what I hear from my teacher friends:

* Administration overload (government compliance type stuff)

* Developing brains aren't always fun to be around

* Parents expect to outsource child rearing to the school and want to be catered to in their unique sensibilities while the teacher wants to focus on what's best for the kid and the class

* Even here in Europe, an increasingly litigious attitude, where any school decision you disagree with is escalated and finally prosecuted. This increases the box-ticking, cover-your-ass sort of administration

This has some of the classic ingredients for cooking up a burnout:

* Investing emotionally in your work

* Feeling like you're letting people down constantly

* Being expected to do things that go against your personal ethics

* Spending a lot of time on things you consider are wasting your time