This is what I remember of the song. I sang it in school as well....

An Irish Ballad

Down in County Kerry on the Emerald Isle
Two lovers made a vow to be true
And Patrick O'Leary told Molly Malone
My darlin' I'll come back for you
When the warm sun of Kansas makes the grain grow tall
My darlin' I'll come back for you

Sail away my darlin' to America
I will wait in Ireland for ye
When the warm sun of Kansas makes the grain grow tall
My darlin, you'll come back for me

Patrick had a brother who was already there
And together they worked on the land
He built a little cabin and planted a rose
For his Molly, sweet Molly Malone
And his dreams were an echo of the song in her heart,
His Molly so far far away.

Sail away my darlin' to America
I will wait in Ireland for ye
When the warm sun of Kansas makes the grain grow tall
My darlin, you'll come back for me

A rage of Scarlet Fever started down in the South
And Kansas wasn't far away
And Patrick O'Leary was buried in June
Near the rose that he planted in May.
But his dreams were remembered in the heart of his love,
His Molly so far, far away.

Sail away my darlin' to America
I will wait in Ireland for ye
But I'll n'er love another til the day I die
When my darlin, you'll come back for me.


That is how I remember the song...although I can't seem to get the whole thing in my head. Let me know if this sparks any memories.