If you mean what sized Basketball, then it is a size 6 for any girls playing representative basketball, and size six for boys playing representative basketball until under 16's at which stage they will up-size to a size seven ball. in some organizations grade 1 and 2 use size 5 but the rule varies.
In my league (Sierra Youth Football & Cheer): Mighty Mites: pee wee size football Jr Pee Wee: junior size football Pee Wee: junior size football Jr Midget: youth size football Midget: youth size football
Junior Women's Hockey League was created in 2007.
International Junior Hockey League was created in 2005.
Metro Junior A Hockey League ended in 1998.
Metro Junior A Hockey League was created in 1950.
National Junior Classical League was created in 1936.
Minnesota Junior Hockey League was created in 1974.
Canadian Junior Football League was created in 1890.
Saskatchewan Junior Hockey League was created in 1968.
Continental Junior Hockey League was created in 2010.
Junior League World Series was created in 1981.
Eastern Junior Hockey League was created in 1993.