While Alonso had developed close relationships with many of his students, Joel was looking for something the others weren't: a father. He was also desperate to get out of a rough neighborhood where he faced intense pressure to join a gang. "Where I lived, you did what they did or you were against them," he said. One of his two childhood best friends ended up dead; the other became a fugitive.

"I didn't want to end up like that," Joel said, "and I saw someone who cared about me and wanted to help me."

For a new single dad, there had to be rules. Joel would attend the public high school in Weehawken, the town next to Union City. He would do two hours of homework every night before he could leave the house, and he would have a strict curfew. Alonso also wanted him to memorize a page of the dictionary each day. He didn't get very far.

No matter how Joel tried, he could not understand chemistry. Alonso made him take it three times. They sat at a diner for hours at a time, father helping son with homework. On graduation day, Joel retook a chemistry exam in his cap and gown, then waited anxiously to see if he'd passed and could collect his diploma. He did. Alonso made him commit to at least one semester of community college. When Joel dropped out after that semester and got a job selling vacuum cleaners, Alonso insisted that within six months, he figure out a viable vocation.

So Joel enlisted in the National Guard and was sent to Aberdeen. After eight months, he emerged with training in small motors. Later, he returned to Maryland because a friend needed a roommate - a convenient choice for Alonso, it turned out.

Now 33, Joel lives on his own in Frederick and works as a mechanic. He comes to Baltimore every few weeks to visit Alonso, and the two regularly drive together to New Jersey to visit family.

"I don't feel like an adopted kid," he said. "I really, really feel like I'm his son."

Seeking challenges
From Berliner, Alonso moved on to another school to oversee a regional bilingual program. Over time, he became more and more disillusioned as he watched his students make progress, only to slip when they arrived in Newark's dysfunctional high schools.

After 12 years in the classroom, he decided to make a broader impact. He applied to Harvard's Urban Superintendents Program and was among the few accepted with no prior administrative experience. Being an alumnus didn't hurt, but program director Robert Peterkin said Alonso's application stood out because of "the commitment he made to teaching the most vulnerable students and the clarity of his view on how to change public education."

"His personal story was compelling," Peterkin said, "and he tied it to the possibilities for all children to learn and succeed."

At Harvard, Alonso interned for Peter Negroni, then the superintendent in Springfield, Mass. Negroni said he had nothing to teach Alonso about instruction and put him in charge of a group of schools.

"He'd go in a classroom and be able to decipher what he saw so well and then put together a plan to help improve that teacher," Negroni said. "It was just unbelievable. He's the best at it I've ever seen, and I've seen a lot of people."

But in the political arena, Negroni discovered, his intern had work to do. "He was anxious to get the instructional work done, and you can't do the instructional work without doing the political work," Negroni said.

While still working on his dissertation, Alonso was offered three jobs within the New York City Department of Education in 2003. He accepted the position of chief of staff to the deputy chancellor because it would put him in the middle of everything. After serving under two deputy chancellors, he moved into the position himself.

In Chancellor Joel Klein, he found someone who shared his conviction that anything that might help students is worth trying. Alonso said his direction from Klein was "Run, Andrés, run."

Which he did.

Alonso's secretary would try to get him to slow down long enough to eat lunch, but typically, he ran on adrenaline and waited to eat at night. He visited schools almost daily and though he had a long commute home to New Jersey, his BlackBerry was always on.

"I would start getting e-mails from him at like 4 o'clock in the morning on things that he needed right away with great accuracy and rigorous analysis, and he needed them now," recalled Brian Osborne, who was his chief of staff and is now superintendent of the South Orange/Maplewood School District in New Jersey. "There were also things he had asked me about at 9 o'clock the night before, and he wanted to know what was taking so long."

After completing his doctorate in 2006, Alonso felt ready to take on a district of his own. But it had to be a place where he'd have the power to make changes for the right reasons, not because of politics. And the bigger the challenge, the better.

In the spring of 2007, he got a call from a search firm hired to find the Baltimore schools a new CEO. He didn't submit an application but agreed to a confidential meeting with school board members at a hotel outside College Park on a weekend when he was traveling to meet Joel.