Parents Who Don't Remember Sneaking Makeup Into School Horrified At Wal-Mart
First off, I don't think you can say that "Disney Princesses" or "Crayola" is a MAKEUP line. I'm guessing (since I don't do walmart) that it's like the Barbie stuff we used to have - very light cologne, bubble bath and maybe a lip balm. So comparing a line that has mascara and blush and eyeshadow to something like that is just silly.
To answer the title of the thread, I think we were 7 or 8 when we started buying nail polish and 9 or 10 when we got into the Lip Smackers. Plus I also bought the occasional face mask or whatever. But that was it for a LONG time. If I had ever put eye makeup on at age 8, my mother would have had a coronary.