In 1960, Clio, along with seven other schools from around Genesee County left the GCBL to form the Big Eight Conference.
Clio remained a member of the Big Nine Conference through the end of the 2004-05 school year, when the district applied for and was granted membership into the Flint Metro League for competitive reasons.
The school has had several individual state champions in boys' wrestling and girls' cross-country.
Recently the boys' cross-country team took second place at the Michigan State Spartan Invitational (2012).
Sheppard, who was the public address announcer for the Mustangs for many years, was killed in a collision in Chesaning, MI in 1990.