Here's a colorful keyboard poster for your school's computer lab. It measures 6 feet long. I'm including a high-resolution JPG and a PDF file so that you have options when printing.
You can print this on a large-scale banner printer if your school has one, or you can tile print it and assemble it yourself. Alternately, you can send it to a professional printer to have it printed on vinyl or another material.
I hope this is as useful for you as it is for me in my lab!