The comedian and activist told reporters Tuesday that he supports emergency financial manager Robert Bobb's expansive plan to turn around the district.
The two will go door-to-door later Tuesday, urging parents to keep their children in, or return them to, the district. Cosby also will attend a rally at Henry Ford High School.
Bobb is pushing the district's $500,000 student retention campaign called "I'm In."
Enrollment dropped below 100,000 last year, and Bobb has budgeted for 83,777 students this fall. Classes begin Sept. 8.
Gov. Jennifer Granholm appointed Bobb in March to fix the district's finances.