(Foreign folk, please don't get the impression that all English schools are this way, but...)
My school was like that too. My brother was threatened with a knife in "food technology" too. Various teachers were beaten up, and I remember one time, an enraged pupil holed himself up in the woods at the back of the school with an air rifle. Someone also shot contestants in sports day with a BB gun, just for laughs. Fights were fairly regular. There were a few mental cases who tried to kill themselves by hanging themselves from windows and doorknobs and lying on the floor. They just passed out and teachers came. Some retarded townie kids from the lower school often went around just randomly beating the hell out of anyone - they were so small, but there were loads of them. I have to confess that when I got angry I actually knocked two of them out.
I didn't know my own strength. Nearly all of this happened in the latter two years of school, when the school had a new, and slightly stupid, headteacher - the previous guy had been a massive, Irish, gravelly-voiced man, who scared kids into doing what he wanted, but was actually a lovely chap.
It was quite a horrible school.
Not many problems with drugs though.