DD started shaving in 6th grade. She was an avid gymnast and it wasn't unusual for the darker haired girls on her team to start shaving in 5th grade since they spent so much time in leos.
6th & 7th grade is the norm. I can remember when I was in 7th grade and everyone was making fun of a girl in our PE class because she had black hair and very dark, hairy legs. No one wanted to hold her legs during the physical fitness tests (sit ups, leg reaches). I held her legs along with the PE teacher, who didn't do anything to shut the little a-holes up, and then I got made fun of for 'mating with Sasquatch.' The girl's mom was very strict that she couldn't shave until HS. That just seemed like such a weird rule to me.