JRP Girls Knee Sock. The size is woven into the bottom of the sock for easy sorting. These run bigger in the foot than some other brands but shorter on the leg. The cotton is a nice thickness and the quality is good. JRP knee socks are very popular. The average high school girl and woman wear size 9-11. If a girl or woman have a large foot or are tall they should select 11-13. 70% Cotton, 27% Polyester, and 3% Spandex.