I don't even raise my voice these days. The things i've seen over the years though, big blokes screaming nose to nose at little kids, teachers planning on who they want out next and how they can wind them up so they do something worthy of exclusion, schools with 'hit-lists' of kids they want to get rid of. Some schools make up their mind before the student even arrives based on their previous record.
What is currently seen as good practice in behaviour management is an absolute disgrace. I really would like to do a panorama style hidden camera documentary on it - you'd be shocked!