I second the belief that they are speaker connections. My old school ('60s built) had two sockets which looked a lot like these - one either side of the wooden stage. When we had foreign language exams, I remember a cassette being played through a stereo system and the teacher would get the speakers out, put them on the stage and hook them up to these sockets.
When the school was knocked down a load of pictures were taken of inside but for the life of me I can't find ones of the dining hall.
When the school was knocked down a load of pictures were taken of inside but for the life of me I can't find ones of the dining hall.