In the 1968 presidential election George Wallace receive nearly 10 million votes as a third party candidate while carrying 5 southern states. Michigan, meanwhile, was struggling with segregation all its own, especially in Detroit area schools. The NAACP argued that this was the result of both government policies and redlining--private banks denying loans and mortgages to minorities especially depending on where they were looking to buy. Initial success of NAACP lawsuits lead the courts to implement "busing"--simply put, transporting students from one school district to another to create more racially integrated schools. A busing program in Pontiac lead to the creation of the National Action Group to protest busing, a visit by and arrest of American Nazi Party leader Patrick Tifer, and the conviction of former Grand Dragon of the Michigan Ku Klux Klan Robert E. Miles and four others for charges related to destroying empty school buses. Still pro-segregation George Wallace would win Michigan's 1972 Democratic presidential primary with a narrow majority. Ultimately, Milliken v. Bradley would see the Supreme Court end busing from Detroit's (white) suburbs, ruling that the de facto segregation was not an explicit policy of the 53 school districts involved, so the government was not required to address it.

While much of this happened after the yearbook photo would have been taken, the underlying tensions and Wallace's presidential run are likely the link you are looking for.

https://www.michiganradio.org/post/moment-history-sealed-detroit-schools-fate

http://blogs.detroitnews.com/history/1997/05/03/irene-mccabe-and-her-battle-against-busing/
https://www.nytimes.com/1971/10/21/archives/five-are-indicted-in-pontiac-bombing.html
https://www.nytimes.com/1975/12/03/archives/5-years-of-busing-in-pontiac-mich-gains-and-losses.html
https://www.oyez.org/cases/1973/73-434