I regret that I only have a few moments here, but before this discussion gets too deep in, I want to mention that my objection to "direct to parallel" lies not on the technical end. There are great drills, exercises, and progressions that can be--and often are--used in many so-called "direct to parallel" lesson plans. And for the most part, they will work fine on 90 cm skis, although I prefer skis a little longer and more "real ski-like"--something in the 115-135cm range.
My objection is philosophical. Simply calling it, and advertising it as, "direct to parallel" ingrains the very false illusion that "parallel" is somehow akin to "good skiing" or "expert." It isn't. "Parallel" is, of course, simply a geometrical arrangement of the skis, and in truth, expert skiers' skis are only sometimes parallel. Experts' skis also diverge, and converge, usually with purpose, sometimes just incidentally. "Parallel" is no more a guarantee that a skier is skiing well than the type of skis the skier is on--and the vilified wedge is not a guarantee that a skier is skiing poorly.
What is important--and of course, much more difficult for the average newcomer to see and understand--is the movements, intents, and tactics that underlie the turns. There are wedge turns that involve every fundamentally critical component of "expert skiing," and there are parallel turns that involve every error in the book. And even the world's best skiers make wedges and so-called wedge christies often, particularly when skiing very slowly and making tight turns (as in a lift line, for example--or a beginner hill)--even when they are not attempting to brake or wedge.
So the problem that often arises in a "DTP" lesson is that the student may be taught all the correct things and, in fact, make all the correct movements, but then a little wedge sneaks in while turning. Because of the association of "parallel" as the goal, and the vilification of the wedge, the student thinks he must be doing it wrong, To "correct" the error, he makes a very wrong movement or two to force the skis parallel. And on it goes. Despite the best of intentions, "Direct to Parallel" often leads to some of the worst bad habits and dead ends in skiing. (No, it does not have to.)
Furthermore, any argument in this area only relates to teaching turning. Turning, while it is the fundamental "thing" in skiing, is hardly the only thing we need to learn or teach. Even the fastest race cars need good brakes as well.... You do not need to teach a wedge to teach good turning, and the wedge itself is incidental and non-critical in beginner turns, as in expert turns. That much is true. You also don't need to teach "parallel" to teach good turns. Wedge and parallel have nothing to do with it!
It is far more appropriate and important as an instructor to recognize the fundamental movements of a good turn than to obsess over whether the skis are actually "parallel" or not. Likewise, it is critical that we don't saddle our students with "false goals" that in fact have nothing to do with "good" skiing whatsoever, and help them understand and develop the movements, skills, and tactics of excellence, right from the start. Those movements are the principle elements. "Parallel" or "wedge" are merely characteristics. I'd love to have time to go more deeply into what some of these principles are--and we have had many discussions about them in the past--but it will have to wait this time.