This was also my thought however where ever the image projects, i.e. the place the students would also interact with the projected image, would need to have direct line of sight to the lens and optical light source. For example, if a K student needs to go to the whiteboard to interact, the projected image would need to be situated in such a way where they would be able to reach at least the middle of the image at their height. The angle of the lens would need to be lower thus when they turned around away from the board they could easily glance up and into the lens.