There is a HUGE difference between making a copy of a student's work to use
as reference or making a copy of an image from a book (if you cannot find the
image for purchase elsewhere) to use for education purposes and STEALING
someone else's work to make a profit.
I am a stickler about not letting my students use images, other than their
own, in their work. I will rarely even let them look at a magazine much less
use an image from one. I don't allow them to copy cartoons and call them
their own, etc. I do not think anyone here is casual when it comes to the
idea of an artist's ability to protect his/her own work.