We used to sing the Beatles 'Maxwell's Silver Hammer' at one school I went to. I often wondered which teacher there first thought 'Hey, let's get them to sing a song about a homicidal maniac!'
As for the Yellow sub comment, can't verify if it's true, just something I picked up in my travels somewhere.
That's the one mate! Almost as good as 'Knees up mother Brown' which we also sang - if you think about the wording, it seems to be a song about raping a housewife...