There's a movie I saw part of on TV back in the late 90s, these are the details I can remember:
- It has to be old enough to be on British TV around 1997, but it wasn't too old as it was in colour and there wasn't noticeable film grain.
- It was in English, but I don't recall if it was American or British, I'd guess probably British as:
- The students had uniforms which included a dark blazer
- There was a scene in which they lock a teacher in a chemistry lab and gas him to death
- It's not if... (1968)