Robert Reed played a high school music teacher and orchestra conductor in "Two Loves for Jenny," which aired on 10/27/82. It's now available on DVD. Read a review here:

http://www.sitcomsonline.com/afterschoolspecials19821986dvdreview.html

Also, Christopher Knight and Eve Plumb were in an earlier volume. They were in "Summer of the Swans," which aired on 10/02/74. Eve just has a cameo in it, but Chris has a pretty big part. It was released on DVD last year. Read a review here:

http://www.sitcomsonline.com/afterschoolspecials19741976dvdreview.html