The list is unimportant. Juding by the samples of "Erie Canal" and "Johnny Comes Marching Home" we get the drift.   It is only a guess since we haven't read the list, but I am sure the songs are those which 30 or 40 years ago would have appeared in most music collections.

My kids go to the same school system that I went to. In the early 60's we were singing songs like those above. I still remember one teacher bringing in boxes of Goober Peas as she taught us the words to the song.

When I looked over some of the songs that my daughter was singing, I did not recognize most of the songs.   A lot of the songs were written by modern authors, many primarily for the specific song collection that the teacher was using.   I also recognized that these songs were designed to teach specific musical lessons rather than being a song designed by the folk process. Songs would be created to teach harmony or simple scales - it is often easier for an educator to make something up to teach instead of doing their homework to find a song that would fit the example. Sometimes it is cheaper to - remember that many of these "folksongs" have copyrighted arrangments thanks to the folk revival.

I am sure that budgets have a LOT to do with this. But I also think it is changing cultures. I remember learning folksongs on the old Captain Kangaroo TV series.    When my daughter was young, she watched Barney, that big purple dinosaur that was soundly criticized. I was happy to see that on that show at least, Barney often sang what we would sort of recognize as "folk" songs.   My son, six years younger, watches the shows that have followed in Barney's tracks - shows that play inspid original tune that sell products rather than ideas. The times they are a changing... unless you use VISA or Mastercard.

Ron