The photos look to me like they are from 1975, and I think the play was Snow White and the seven dwarfs.
My sister, Roberta Neill, and I are both in some of the picture and she left Elmgrove in 75. In the 76 concert I was Ada in Tom and the water babies. There doesn't appear to be any pictures of that.
By the way, the site is great !!
Sue Lawson (nee Neill)