I am not a trained instructor, nor a terrific skier, but I have gotten lots of people of all ages started on skis, including my own kids. I never used a leash on my kids, even when they were 3 or 4. Instead I skied backwards in front of them, staying about 10 feet ahead. If they lost control, they would gently crash into me, with both of us remaining upright. But the vast majority of the time they were on their own, with no adult crutch or support. I found that if I made gentle turns, they would follow me without even realizing they were turning. They were also forced to learn to stop on their own, without a parent putting on the brakes.
I agree completely about the No Poles rule. When I first took my best friend skiing, he was mad that I wouldn't let him use poles... until late in the 2nd day, when I finally gave them to him. He decided he was REALLY glad he hadn't had poles to worry about any sooner! When I first give my student poles I have them hold both poles in both hands, out in front, parallel to the ground. Keeping the poles perpendicular to the fall line helps keep the upper body in that position as well, and helps curb the tendency to finish a turn with the upper body pointed uphill.