My daughter took TKD and lost interest after 3 months, and didn't want to go back after 6 months. Here is some things she despised - and advice for teachers.
Funny enough, these were all things I told instructors...
1) Don't give 6-7 year girls 20 pushups. IT"S POINTLESS! You might as well ask the 40 year old father to do an oversplit.
2) Don't touch kids if you don't have to. If you want to change a kid's stance, just tell them. Don't kick their legs out with your leg.
3) As Ricardo Montalban says, "Smiles everyone, smiles!" This isn't the military. No one has to be there. Remember that if the kids don't find it fun or happy, they won't continue.
End of rant!