Michigan 's lack of preparation of children for college could limit the state's access to a competitive workforce and weaken its economy over time, according to a study released by the National Center for Public Policy and Higher Education. Over the past decade, the number of high school students in the state who enroll directly in college has declined by 7 percent, the report says. The national average is 2 percent. The study gave Michigan high marks for giving residents sufficient opportunity to enroll in post-secondary education and for economic and civic benefits the state receives for having a highly educated population. But Michigan received an "F' for affordability of college education and a 'C' in preparation of students for post-secondary education.