Burly, bearded, direct in style and bold in substance, Baltimore schools CEO Andrés Alonso changed the course of city education during his six-year tenure here. Graduation rates rose, as did test scores, enrollment, and hope.

The 56-year-old Cuban-born, Harvard Law School-educated bachelor, known for his around-the-clock work ethic and high visibility in the school system—as well as his sometimes tough decisions, such as closing schools—leaves on the heels of a historic $1 billion agreement with the General Assembly to rebuild the city schools' infrastructure. Not that it was all honor-roll stuff: He also battled a cheating scandal and fiscal mismanagement questions.

A former lawyer who quit to teach special education in Newark, NJ, for 12 years before coming to Baltimore, Alonso's commitment to city children was never doubted. But when he announced that he was quitting in the middle of a four-year contract to care for his aging parents and accept a Harvard professorship, the city—and school system—was caught by surprise.

Rumors are he could be the next chancellor of the New York City school system. Meanwhile, a permanent replacement has yet to be made.

“Dr. Alonso sparked the sense of urgency and the collaborative spirit that now has an entire city rallying around its kids, in a way we haven't seen before here in Baltimore."—Neil E. Duke, Baltimore City School Board President, in a press statement