The War Game
Our English teacher (who also ran the cinema club) got his hands on a copy and showed it as part of an antiwar "Season" (three weeks of themed films).

It really did scare me shitless and not in a Jump oh my god it's freddie way. It was genuinely scary.
(porkylips looks better as the sun goes down., Thu 22 Apr 2010, 8:57, 2 replies, latest was 16 years ago)

Now that you mention Freddy
I saw Nighmare on Elm St. 4 when I was about 10 and didn't sleep well for the next three months or so.
(ConanTroutman thought we would free the vulture, Thu 22 Apr 2010, 9:04, Reply)

I have that on DVD - assuming you mean the 'Drop da bomb on Sheffield' film
It's still chilling, and when my children (then 16 and 13) saw it they wanted to take it to school. My son asked if it could be shown but request declined.
( Larry Vest One day at a time, sweet Jesus, FFS., Thu 22 Apr 2010, 12:14, Reply)

No, I think that one is Threads from later on (1980-something).
That was good too but originally The War Game was considered too bad for broadcast. Too realistic with the black and white make up. The injuries simulated were copied form MoD files. Horrific.
(porkylips looks better as the sun goes down., Thu 22 Apr 2010, 12:22, Reply)