It might have been a Cirkut.

Our school photos were done with a Cirkut. We would be sitting or standing on benches arranged in an arc of a circle - so we appeared to be in a straight line and the school building behind us appeared to be curved away from the camera.

If you were on the back row at camera left you had the opportunity of being in the same picture twice. After the camera had passed you, you ducked down, ran behind the rest of the pupils, then squeezed in at camera right, hopefully before the camera reached there.