I've always felt that if a teacher or company has particular requirements of its students or employees that they provide the tools needed.

Art is a tricky subject to place requirements on the tools you use to create with, particularly if they demand you use a particular company's products. If the desired effect is shading then the true test of artistic ability should be able to create the effect using whatever tool is at hand, not a particular brand or type of tool.

Since it seems we're talking about low level art classes for beginners, it's even more ludicrous to require they purchase specific art supplies.