In almost 40 years as a flying instructor, both military and civil, I have often taught the selection of flap in the turn - when you are flying an oval circuit, as in the military, you don't have much option. I know of no occasion when a student, even on first solo, has lost control, stalled or entered a spin as a result of selecting flap in the turn (or, come to that, of any instance of flaps extending asymmetrically).
Of course, Alister, if you are suggesting that civil students are not as capable of learning to do this safely as military students of the same experience, who demonstrably are, that is an interesting statement on the ability either of civil students or of civil instructors! Not, I hasten to add, a statement with which I would agree.
At the same time, I have never taught a student to do clearing turns before steep turns - utterly ludicrous!!