In the mid 1950s.
The earlyist song I remember from kindergarten:

There was a crooked man who walked a crooked mile,
He laid a crooked sixpence upon a crooked stile. . .


I remember these from elementry school:

Old Black Joe
Camptown Races
Cape Cod Girls
Reuben
America The Beautiful
Tingalayo

And holiday songs:

Over The River And Through the Woods
Angels We Have Heard On High
Oh Hanukkah