I can't find a resource to answer this question. Looking for the size of the basketball used by boys in the 7th/8th grade by state.
Ebay listing says the 28.5" Spalding-1000 is the official size for women and boys 12 and under.
Although I'm having trouble finding records for many states, so far I've found:
Alabama & Alaska use NFHS rules, but don't specify ball size for Junior High. Probably 29.5".