They're dealing with probation, pregnancy, drugs, you name it. The system is designed to burn you out if you're too conscientious in care of the kids. It's stacked against you. I know I was a good teacher. I don't know any more if I can even be a decent husband or father.
Teachers commonly describe the burden of guilt and neglect of their own families.
I put more time and effort into my students than into my own children. And when I do spend time with my kids, I'm often correcting their behaviour and trying to control them to live up to my perfectionist standards. The stress on the family can become extreme when sick leave has been used up. And if it doesn't come through, I'm just going to have to go back to the classroom, even if it ruins my health for life. Of course, some of the effect of teachers' work stress on their families is inevitable.