The lyrics I sang in grade school in the late forties went like this:
Rosy, Poly blue eyed Molly, Molly, April is the time for folly, folly, who can stay at home all day while jenny wren is building in the willow.
Cant remember the second verse completely.
But, I do know the lyrics that some have posted claim it went like this:
Rosy Betsy blue eyed Molly Molly, which is wrong.

It was Rosy Poly blue eyed Molly.
And why? because Poly rhymes with Molly and Betsy does not and that is the way all song lyrics are. Sing it both ways and see for yourself which sounds right.