Now, if you're a teacher working in a UK state school, this particular web-page is probably unnecessary for you. I'm going to outline the problem with teacher stress, but you already know that, don't you?
In our results-driven society, the activity itself is not precious - it is the end-product that is evaluated and esteemed. How does that make you feel? The thing you love doing has no value. This sense of being under-valued is in itself stressful, but that is compounded by a heap of other stress factors. Firstly you have to deal constantly with people who are by their nature not-very-calm, that is children, and near-adults. You also have colleagues who are struggling to achieve their work targets, and frequently working in areas where they lack competence (I am talking here about man-management and data analysis, not pedagogy). Your job itself has stress factors associated: long hours, irregular workload, and frequent interpersonal conflict.
It is no wonder that teachers follow - sometimes lead - the trend in modern industrialized society regarding mental health: a trend which according to almost all indicators is downward. People are simply more anxious, and sometimes more depressed, than ever.