Rode today, it went really well. I even put my son up on her for the first time, huge smiles. He's had 5 lessons now on 5 different horses, and is doing wonderfully. Is even posting on the correct diagonal!
The reason for this is so that they develop a good seat. I do not care what the rest of them is doing (within reason) as long as they can sit deep - the rest will come very quickly once this is established.
The children yesterday were trotting, reins in one hand and front of the saddle in the other, pulling the front of the saddle off the horse's back. This makes them lean back and inclined to put their feet to far forward but they learn to sit deep and when they let go of the saddle they will be sitting up and as I said, they then can be corrected to the right position.
It also teaches them the 'back' is a safe position and anything untoward they will lean back rather than forward.
I want the novice to feel the horse, learn to relax into him, and only after they are naturally feeling comfortable do I start to tidy them up.