The thigh high socks must be really thigh high, even for a 6-foot girl. I can't understand that some knee high socks are also boasted as thigh high socks. Knee high socks and thigh high socks with short skirts or boots are completely different styles. Their thermal performance is also completely different. They are basically two kinds of socks.
The thigh high socks should be longer than expected. It's not for that the girls will still grow taller, but that the long thigh high socks have better compatibility. When you are not sure about the exact height or thigh size of yourself, longer thigh high socks will adapt to more people.
Longer thigh high socks are not easy to slide down. Generally speaking, the longer the thigh high socks have the wider elastic part on top of socks. This is unexpected that they can have more parts in contact with the thighs, and also that they have more friction, so that they will stay up well.
Kayhoma thigh high socks are extra long. They measure 28 inches from the bottom of the foot to the top of the socks. Even for a girl who is 6 feet tall, they are all real thigh heights. For little girls, there is no problem at all, just stretch them not too much, then they can perform very well.