I guess my main problem right now is that they all have chair seats. It's terrible, and I don't know what to do to fix this, besides tying their legs back. I'll constantly remind them, I'll constantly move their legs, show them, try to explain what I want them to do and why but nothing seems to be working.

I guess what I really need is a better way to explain to them leg position, or some exercises I could have them work on to improve it. None of these people has ever had a lesson in their lives, and I've never really given lessons, so it's hard for me to explain what I want them to do in a way they can understand, and it gets really frustrating when they keep going back to a chair seat, or just don't understand what I'm trying to tell them.