Pick a colored patterned image online

Set up the glass cups in front of the computer screen on the mirror. 

You will need to have it sitting on something that will elevate it to the height of the computer monitor.

Set your ISO.  Even though it is dark in the classroom your camera will be reading the bright light from the computer monitor.  Set it at about 400

Set your Aperture to F/8

Scroll your shutter speed to the middle.  If it is below 1/125 of a second, increase your ISO

Crop out anything that is distracting from the image.  You should not see the monitors edge.

Edit so that all of the colors pop.  

If doing a black and white image make sure the whites and blacks are very strong.