Here is another one, which belongs to the second group mentioned by Iona & Peter Opie (The Lore & Language of Schoolchildren): THE WOMAN IN A CHURCHYARD, or, as I know it:

A WOMAN STOOD AT THE CHURCHYARD DOOR

 I learned it when I was in the Wolf Cubs (as they were called then) in the early '60s.   The song was sung only at Summer Camp, and we all had to promise not to tell the younger ones about it; that way they'd jump out of their skins like we had, when it was their turn to hear it.  It made a big impression on me, and the words and tune stuck in my mind after only one hearing.

A woman stood at the churchyard door
Oo-oo-oo-ooh, a-a-a-ah
As many another woman had done before
Oo-oo-oo-ooh, a-a-a-ah
Saw three corpses carried in
Oo-oo-oo-ooh, a-a-a-ah
Very long and very thin
Oo-oo-oo-ooh, a-a-a-ah
Worms crawled in and worms crawled out
Oo-oo-oo-ooh, a-a-a-ah
Went in thin and came out stout
Oo-oo-oo-ooh, a-a-a-ah
Woman to the corpses said
Oo-oo-oo-ooh, a-a-a-ah
"Will I be like you when I am dead?"
Oo-oo-oo-ooh, a-a-a-ah
Corpses to the woman said:
(SCREAM!)

Each line was sung quietly but emphatically; the refrain, with which everyone had to join, was very quiet.

In the late '70s I played with an electric folk band in Sheffield, and we did the song a number of times at student venues -they jumped just as I had when I was 8 years old.  

I should mention that I had the song from a Mrs. Joyce Riddle, originally from Yorkshire, so perhaps this version was from there.  The version quoted by the Opies, incidentally, is from London and is a recitation, not a song.  The tune that I have is one of those trichord ones that belong particularly to children's and ritual songs (see also SOULING SONG, here, though I suspect that the tune given is taken from a commercial recording, and possibly a harmony line has inadvertently been incorporated into it at some point), the compass being in this case a minor third.  Because I can't resist it, I'll post the tune to the midi site.

Malcolm