It has been stated, and supported by research that the great Leonardo da Vinci used this tecnique! If anyone running a art clas has a problem with that, remind them that Leonardo is the all times best artist -and engineer ans sci-fi writer that ever lived - by far!
It has also been suggested that Leonardo was able to make photograps with his camera, by some kind of tar process I'm told, but was not able to fix the images, wasn't it Talbot who did that? (Daguerre was on a totally different track with a process that would have been banned today within minutes, utilizing mercury vapors.....)
To my mind, using a camera obscura would actually enhance a drawing class, since it frees one from mundane tasks, allowing more time on the details, and the details is what matters in drawings.
Compare this to a class in math, 15 years ago calculators was banned, and the pupils had to climbe ever mountain in the learning process by hand. Today they all use calculators leaping by bounds from peak to peak in the process.
Its not comparable, they don't learn to do small change in their head, but really no nedd to since the change comes up automagically on a screen at counter!
I'd say go for camera obscura and revolutionze drawing class!
If I had one of those new desk-screens, i'd pick up drawing & painting in a minute! The end result is NOT a photograph.