Have you seen the free how-to-draw videos from Shoo Rayner? He just posted a Mayflower drawing video which would be great for middle and high school. I love how he shows the whole drawing process, from a light pencil sketch to a finished pen drawing.
Shoo has lots of other fabulous drawing videos. If you have students who love to draw (and parents who allow them to access YouTube), please let them know about these fabulous videos. They will stay very busy over the winter break!