I remember being in middle school for the original nationwide "environmental teach-in" on April 22, 1970, or the first Earth Day. I seem to remember watching a movie on ecological threats in the gymnasium with the accompanying music being Marvin Gaye's
"Mercy Mercy Me (The Ecology)." However, I believe that song/album came out the following year in 1971 so the assembly I am remembering must have been from the second or third Earth Day.
https://www.youtube.com/watch?v=CShUISLYLGY
https://www.youtube.com/watch?v=CShUISLYLGY