Thanks for the help!! After I thought about it, I had a graduation dress that had the same princess lines this dress has and that was in 1968.
I don't think it has been shortened. I had my mother check it out also, she is a dressmaker, and it looks like the original hem, only about a 2" turn up. The skirts got shorter and shorter as the seventies approached, but they started out just a few inches above the knee, I do remember that now. We had to have them measured at school at first, and then later it was no holds barred as the dress codes were lifted by the time I graduated HS.
thanks again, as I got to second guessing myself!!