Is awful for everyone concerned. I have taught in a difficult school and been attacked by pupils and found myself in tears after classes. Teaching can be very, very stressful. If you have day after day with horrid children and no back up. Someone mentioned mob mentality and it can be so threatening, I have heard of one teacher tell of someone she once worked with having a heart attack in class, and being found with books piled on top of him that the children had thrown as he fell to the floor. Awful for teachers to 'teach' in these environments and awful for pupils to have to go to these schools.
I now have a strong head, and she works us hard and my school is far from the perfect place to teach, but mostly it is a nice place to work, the truely horrid children are normally dealt with. I don't want people to be under the impression that all poor schools are anarchic, strong headteachers is the key.
The teacher should have walked away, if you have lost control you are no good in the room, I have walked out of classes before, it is pretty terrifying to be stood in front of 30 kids you are responsible for and not be able to get control.
I don't know what the lesson to be learnt from this is. Maybe we need to be more cautious when people return to work? I also think that teachers who are being bullied by the children, which seems to have been happening here needs to be dealt with more effectivly. Teachers should be able maybe in extreme situations to be able to refuse to teach a child or a class if they feel unable to.
I think lots of teachers find returning to work after sickness very difficult, I know I have. In 'normal' jobs you can often go back and take it easy for a few days, but teaching is full on and you have to be 100% all the time. If you feel vunerable often children will pick up on that and some will exploit it. They don't see you as a person always.