umm 13 year old girls should probabl use a 28 to 28.5...
A 7-year old boy should use the Junior International Size 5 basketball. The basketball has a circumference between 27.25 to 27.75 inches.
Typically for that age girls use the womens size or 28.5.
breast size should be 36 and stomach size should be 24 and bump should be 36
A youth size ball, size 27.5... and from like 8 to 12 they should use a 28 or 29.
28.5 inch diameter
It depends on the size of the 12-year-old girl.
The size that is right for the body. There is no one size for everyone.