Contrary to most of the views I found on a TES thread, physically assaulting a pupil cannot be justified. Is it acceptable to glass a bloke in a pub because he's shouting abuse at you? No. Is it acceptable to fight back/retaliate to an abusive pupil (who, despite quite possibly being an irritating little shit, is still a child in your care)? No.
You do, however, have to wonder how an experienced teacher, widely regarded as a 'decent bloke', could be driven to such extreme actions. The fact is that any teacher who, for whatever reason, feels capable of hurting one of their pupils should not be in the classroom. Yet, for numerous reasons, many of these teachers are.
Perhaps they find themselves under financial pressure to return to work after sickness (stress-related or otherwise). Perhaps the stigma of showing weakness is too great in some schools, leaving teachers feeling unable to ask for help from their colleagues. Perhaps taking time off for 'stress-related illnesses' is looked upon with disdain by senior management. Perhaps there just isn't enough support for teachers who are good at their jobs but, for whatever reason, sometimes feel unable to cope. Perhaps the number of (also) unacceptable pupil assaults on staff is normalising violence in the classroom.
Isn't it time we stopped dealing with 'perhaps' and figured out why? If it turns out that the teacher concerned did, in fact, assault his pupil, I suspect that the inevitable government inquiry will conclude that what's needed is more screening, checking and monitoring of teaching staff (teaching MOT, anyone?). My fingers are crossed (in vain, I suspect) for a more sensible solution, one that looks at protecting the mental health of excellent teachers who are struggling to cope; let's face it, even though cases like this one are, thankfully, unusual, there are many teachers who could do with the extra support.