Education Projectors Buyer's Guide
To determine the size of screen you need, measure the distance from where you intend to place the screen to the student that will be farthest from the screen. Your screen height should be about 1/6 of that distance. This size is suitable for viewing both video and text. Ideally, the student nearest to the screen should not be closer than two screen heights and the bottom of the screen should be a minimum of 4 feet above the floor for viewing by the entire class.
Screens not only come in many sizes, but they can be mounted in many ways. To position the bottom of the screen four feet from the floor, may require the screen to be hung from the ceiling or attached to the wall.