Just to pick up on and earlier point or two, and make it into a bit of a plan for teaching beginners ........and wrong do-ers frankly, like me.
The point from before was that from outset both styles of xc skiing should be introduced. This is because i characterise correct, efficient classic technique as parallel skating ! The basic proviso being that skiers can learn 100% weight and balance committment to one leg better by doing some ski skating.
For me it was a break through to realise that there are two or three basic mistakes in classic that i make, and many many plodding tour skiers also make and perhaps stick to in defiance of being seen as fancy racing wannabees.
1) sliding and not striding. Badly taught, i slid on skis like toddlers here do and dabbed out with my poles. I grew out of this but still have the problem like a brake pad on my efficiency. Skiing classic or skating is more a stride with an element of lunge in it on classic.
2) not pushing into the glide and holding on to it. Instead i had started kicking back and up, rather than down and across to the new leg, using the whole foot to push off and the new whole sole to land. Also i was terminating my glide too early just to fit my own proposed best rythmn.
I find that i do modulate my kick and land, into toe-to-heel in softer conditions. In harder conditions i keep my vertical rise down. I wonder if these are even right?
3) being stiff and scared of one leg committment. This has been a b ig misconception from not being taught wellx, having people who can kind of preach the right way without being able to either see your mistakes or break down the sub contents of the movements
4) excessive kicking and clapping the ski down
The ways i got over these problems were:
Knowing i was slow and inefficient and wanting to do something about it
Learning to off load one leg and rely on the other in various maneovres for example plough: i often found it mysteriously hard to go into plough but now i unload one ski to break parallel or get out the tracks and then the other follows or i can dab it out by unloading it too.
This is where skating comes in: step turning and lane changing are part of classic racing anyway and given a firm underbase with new snow on top you can skate pretty well on classic skis out the tramlines anyway.
Watching you tube : the weight committment to the new ski about to glide in diagonal is not until the foot is swung well forward and the knee is bent. This need not be very racey but it transforms the weight transfer and stride by elongating the projected , unloaded legs travel while making for a stable landing for the glide. It makes also for a natural transition out of glide to full up hill jogging and also out of diagonal striding into gliding with poling with added intermediate single side kicks.
Clapping skis down is the big symptom of not swinging the foot and knee of the new glide foot far enough forward for the speed. The clap is caused by the foot being brought down early with the ski at a greater angle to the snow, rather than the very shallow angle. In poor glide conditions or steeper hill, the stride may be a little shorter, but is still longer than clapping.
For the new beginner and casual motionist, this is still a valuable observation such that the actual aerobic effort can even b e reduced relative to making good progress in diagonal stride skiing.
So to teaching
The obvious means to teach better stride and glide is without poles, Keith Nicol has the best videos on youtube imho on these exercises. One first exercise he demonstrates is the single ski scooter. This can be then done with new beginners and upgraded by using an oversized ski with better glide or a gentle down hill.
I advocate then doing this out of the tramlines and going right into teaching some skating, before coming back into the tracks. In firmer conditions this may mean using combi boots and both types of ski if budget permits
An order may be then for what could be five days of three to five hours instruction per day:
boots on and jog, loosen off without skis.
Feel the balance of the ski itself on one foot, just how it reacts to being lifted and where it will point
Pad on the spot with two skis to further this.
Crab sideways no poles. Fish bone on very gentle up hill no poles
One ski off, scooter in the spor
Scooter on the middle of the tracks.
Light down hill with run out to run out on the flat. Maybe introduce poles. Walk back up the hill with skis and poles, repeat. Poling then to get speed on the first ten meters and going into full tuck.
Jog and loosen off. Jog with skis on, out of the tracks no poles.
Walk up to a steeper hill with poles. Herring bone on this steeper hill (probably just a diagonal stride hill for experienced skiers)
Plough down and repeat a few times.
Then single leg plough technique.
Plough turn by weighting up the leg and edge.
Wide plough as possible from some speed to a stop if possible or a good bail out speed.
Getting up from deep snow or awkward falls.
Break / day 2
Jogging on skis again, going over to gliding more from the launch.
Skating technique on the flats plus intro to step turn in and out of the tracks
Diagonal technique theory of spenn and stide
Diagonal training without poles, variuous short exercises in and out of the tracks.
Planting your poles and using them to jog with.
Diagonal stride with and without poles, down hill to demonstrate glide.
Fine tuning the stride again to bringing the glide foot further forward.
Jogging / diagonal up a long gentle gradient. Poling in the tracks down hill; repeat.
Skating with poles, single dance basic: flat, up hill and down hill.
Break /day 3
Quick bit of ski skating on a prepared run
Braking using single plough leg again, and skating out the track and into full plough to stop or avoid someone.
Steering in plough on a broad pisted beginner slope for slalom. Loading up the outside leg. Coming in and out of plough, varying plough.
Diagonal practice out of spor and then up a longer gradient
Skiing tucked parallel out of the spor, wider leg, loading and sliding out tail of ski to steer down this long gradient.
Coming out of the spor into parallel wide stance and then plough to reduce speed, and standing up again then into tuck.
Little more skating , gentle down hill or flat.
Diagonal: using the kick off, hip and shoe swing.
More of above diagonal exercises.
Little more skating , double dancing intro.
Step turning round 180' flat turns. Step turning from a downhill in a broad area. Fast small step turns on same course.
Step turning/ skating out of and into the spor.
Poling in the spor
Pole-kicking parellel in spor.
Herring bone up
Steeper downhills in the spor with corners
Steepest dowhill with full plough. Parallell alpine to plough stop for the better students in non icey condjtions
Break day 4
Skating, prolonging glide. Enhancing kick and using hips.
Skate start and then steer into the spor.
Prolonged flat - undulating skate
Classic technique refresher and test of abilities
Tour of 5 - 10km using classic and braking techniques learned so far.
Break day 5
Loosen off, skate , jog etc
Step turning and some exercises on mobility on skis, handball , pick up thjings so on
Diagonal tour 5km with instructor video / observation
Playback discussion at cocoa Break
5 to 10 k with plough turn and step turn involved.
Skate to warm down.
Some fun, maybe laser ski shooting
Throughout you want to find pupils who are good at other sports such as of course downhill skiing or others like skateboarding and anyone who can skate or rollerbladde. They can lead demonstrate in scootering, downhill, plough and skating.
Also you need to pick out people who are learning fast but have a pronounced typical mistake while not stijgmatising the poorest in the group but rather working one to one more with them while the others practice.
Fun and agility is often overlooked for.mature adult courses and reserved for children, but a game of handball or relay pick up balls or blind folded stuff can lighten up thd day and make the participants loose their focus on their boots and theory.
For fit adults a longer tour with a cafe or refreshments laid on should be organised in the week. For a group with varied fitness who cannot be logistically split up, circuits should be used where the instructor can access and monitor any weaker or slower members without being separated from the whole group. Concentric courses are ideal, with a common point for refreshment with a view, cafe or shelter under the trees even.
For schools with a range of equipment, the chance to try skating skis and fell-touring boots and skis should be offered later in the week. Also telemark and randonee skis should be shown in order to demonstrate the spectrum of activities opened up from the base learning.
If there is no natural chalet or hotel gathering afterwards at the centre, then drop any evening lectures or video playback but try to get the day's footage up on youtube and give out links to the likes of keith nichols excellent, simple you tube stuff.