A 3-D printer has an enormous amount of promise for a classroom! I can picture printing math or science manipulatives for students to use. It would be interesting if the students could learn to use CAD to design their own creations. I have had students design shelters in past years. It would be true project learning if students could design and print their own shelters to test. The amount of time it takes to print a creation currently is probably not worth the cost of a printer for student use. If this technology increases in speed and decreases in cost the possibilities are endless.