Nearly two dozen directors of states' largest program have resigned in the last year.
Mayors say the U.S. Department of Transportation pilot program would help boost their local economies.
Minority students became the majority this year, but most teachers are still white. Policymakers are seeking for ways to get and keep more minority teachers.
North Carolina is trying to recruit girls for careers in engineering not only to fill anticipated vacancies but also because hiring more women could make the roads safer.