I'm not fond of the RWS, but when I've taught courses in the past (and when I will teach again in the future) I use it, or very close clones (like recolourations of it). The reason being, everyone in the room is on the same page.
I also have a big festival on the very last day: I bring in my entire collection, and let everyone have a look-through, and I talk a bit about my experience of decks that seem to draw a fair bit of attention. (I have lost decks this way, too: caveat didact!)
I usually will have held a class during the course, sometimes an additional one if it only related to a few people, that I throw in for free, where people are encouraged to bring in any different decks that they might have bought or been given b efore signing up, and I give them some pointers on how to adjust to different decks, using their own deck as a living example. But for the main teaching, choose one deck and stick to it for everyone - and the RWS could have been purpose-made for just this.