I toyed with the idea of doing a PGCE years ago. Decided to work as a TA and Cover Supervisor via an agency, just to get a taster.
Admittedly I worked at quite a few challenging schools, in not the best areas...but the experiences put me off teaching with a vengence.
I got hit across the face with a chair wielded by a 6ft 15 year old when I got between him and the boy he was going for (teacher had already exited the classroom). Had my handbag stolen hidden for several hours. Was sworn at on quite a routine basis.
Believe me I was certainly no pushover, but the basically 'casual' nature of the verbal aggression and insolence took some getting used to.
I can't recall any really overt bad behaviour in lessons when I was the CS, but it felt far more like crowd control than actual teaching - even when it was an English lesson, and I have a good English Literature degree and studied linguistics at Post grad, and could have been of genuine help (rather than being the Cover Supervisor in DT lesson say?).
I did it for months, hoping I would have better experiences, but never did. Needless to say I dropped my PGCE before the course started.
Out of quite a few of our friends who went into teaching straight from university the only 3 left working as teachers are all teaching at selective schools, having regretfully left the state system before they were 30.