I am not a teacher yet but I took a Photoshop class in college and have used it often at my current job. The ONLY way to really learn Photoshop is to use it. If I were grading Photoshop assignments I would grade based on criteria set for the final project such as creativity, the use of many tools (as opposed to just one or two), how effective were the manipulations: for example, if something was cut and pasted, are the edges smooth and believable or is it choppy and sloppy? I think allowing use of the text to do the projects is a good idea. After all, that's what professionals do. If one uses something often enough the book doesn't need to be referenced. But programs are changed and updated so fast we are always refrencing the book.