What is the average pitching speed of 9 year olds?

my son is 9 yrs old and is averaging 40 MPH from 46' w/o pitching from a mound or rubber. I was wondering the same thing. Ultimately the strikes are going to make the difference.

9yr old avg 44-49 mph

9yr old above avg 50-55 mph

9yr old Excellent 55-61 mph