A fire broke out at a home in East Boston Sunday evening, extending to additional buildings and sending black smoke billowing high into the air.

The Boston Fire Department said the flames started at a multi-family home at 263 Princeton Street. There was heavy fire on all three of the home’s porches, which had burned through to the inside.

The fire damaged three additional buildings, the fire department said on social media, and more crews were called in to help. Thousands of feet of firehose were used to battle the flames.

Deputy Fire Chief Steven Shaffer told NBC10 Boston that one firefighter was taken to the hospital by Boston EMS after suffering burns on his hand.

It’s unclear exactly how many homes were damaged by the fire in total, but the fire department said 21 people were displaced. The American Red Cross of Massachusetts assisted them with shelter and emergency supplies.

There was no immediate word on the fire’s cause. An investigation is underway.

Now, research shows the redesign substantially improved the lives of the children who grew up there. The main reason for these outcomes: increased interactions with people who live nearby, the higher income the better.

Compared to kids raised in similar but unchanged public housing, those raised in Hope VI sites are more likely to go to college and less likely to be incarcerated, and earn more money, according to the research from Harvard’s Opportunity Insights, an economic mobility nonprofit.

Researchers found little difference for adults, but for children, each year spent in these renovated spaces increased their adult household income by 2.8 percent. All told, those born and raised there earned 50 percent more over their lifetimes, compared to those who grew up in more isolated and impoverished surroundings.

The new Old Colony complex is fully integrated into the neighborhood around it, with updated architecture, landscaped grounds, and streets running through it. Outsiders regularly walk their dogs or jog through, sometimes even stopping to say hello, Moreta said, likely unaware they’re in the midst of public housing. There are fewer police sirens, fewer safety concerns — and a lot less stigma.

Moreta’s two older children were already grown by the time the project was completed last year. But her younger daughter, Brianny, who’s 14, is benefiting.

“My older children would feel like scum, because that’s how other people would make them feel,” Moreta said in Spanish, through an interpreter.

With the redevelopment, that sense of “otherness” has lifted, she said: “They don’t see us as criminals anymore.”

Public housing was started by the federal government in the 1930s as a way to get people out of overcrowded slums. The buildings were situated on “super blocks” closed off from the street grid to keep cars from driving through, and to keep children safe, said Alexander von Hoffman, a senior research fellow at Harvard Joint Center for Housing Studies.

But eventually, these secluded spaces isolated residents and provided cover for criminal activity. In time, working-class families increasingly left public housing, prompting authorities to admit more single parents and welfare recipients, said von Hoffman, who has researched the history of public housing. Crime and disorder increased, maintenance faltered, and buildings fell into disrepair.

By the 1980s, public housing was in crisis.

Old Colony was no exception. Kevin Weeks, an associate of notorious gangster James “Whitey” Bulger grew up there, and their organized crime ring took over a liquor store across the street.

Moreta’s oldest child, Samuel, was a baby when they moved into Old Colony in 1999. Back then, the complex was row after row of identical brick buildings, encircled by streets that cordoned it off from the rest of the neighborhood. Inside, there were cockroaches and mold, peeling paint and crumbling walls. Homeless people came inside to sleep and do drugs in the stairwells. Gun shots and drunken fights broke out in the street.

At school, Samuel’s rowdy behavior was dismissed as him being a “project kid.” At home, he saw neighbors walking by with a “clutch of a purse,” and he avoided them as well.

“I think subconsciously what it did … is hold off me being able to make connections with certain people sometimes, because I don’t know what their intentions are,” said Samuel, who asked that his last name not be used to protect his privacy.

The government started revamping these deteriorating housing developments in 1993. In Boston, Old Colony was the last of five to undergo a transformation. Housing developments in Cambridge, Taunton, New Bedford, and Holyoke were also part of the Hope VI makeover.

Researchers at Opportunity Insights, led by famed economist Raj Chetty, began studying tax and housing data of people living in these resuscitated spaces. Earlier research by Chetty showed that families who move to higher-income neighborhoods improve their children’s future success, and he wanted to know if bringing opportunity to lower-income families would produce better outcomes, too.

It did — by breaking up the concentration of poverty and increasing social interactions between children of different income levels, said Matthew Staiger, coauthor of the Opportunity Insights study. Cellphone data, Facebook connections, and Census records showed that children who grew up in Hope VI developments were more likely to befriend and later live with peers from outside public housing.

The rate of violent crime in refurbished projects fell by 41 percent compared to untouched ones, national police records show.

Before, segregated public housing likely reinforced the idea that lower-income kids were different and better economic opportunities were not for them, Staiger said.

“Interacting with and befriending kids from higher-income families changes your aspirations and what you think is possible for yourself,” Staiger said. “It changes how you think you fit into the world.”

Occupants of reconfigured housing developments in disadvantaged areas, on the other hand, didn’t experience any economic gains during the same time period.

Not all Hope VI public housing residents are happy with how things have changed. Only about a fifth of residents came back after they moved out during construction, including some who had settled elsewhere in their years away. Others were screened out by criminal background checks and drug tests.

At Washington Beech in Roslindale, resident Meena Carr said the formerly close-knit community is no longer.

“There’s no togetherness,” said Carr, 84, a retired teacher originally from Trinidad and Tobago. “It looks nice, but inside is rotten.”

There are no more bingo nights, no coffee hours. Even the basketball court, formerly used by kids from around the neighborhood, is fenced off with a sign reading: “This is not a public playground.”

Regardless, the Boston Hope VI properties are better off than some because they are all located in or near wealthy, resource-rich areas, said Kenzie Bok, administrator of the Boston Housing Authority, and because the housing authority gets more grants from the city than from the federal government, which has been cutting funds for public housing.

The key, said Bok, is that these new apartments make children feel valued at an impressionable time in their lives.

“It’s going to embolden you in making those connections, feeling like those people and those resources are available to you, that they’re for you,” Bok said.

The economic gains weren’t due to the new mix of residents, noted Staiger, the Opportunity Insights study coauthor. The longer a child lived in a redeveloped property, the better he or she did later in life. Younger siblings who lived in these new spaces longer than an older brother or sister went on to outearn them, Staiger said, and this shows that the environment played a role in their outcomes.

Von Hoffman, at the Harvard Joint Center for Housing Studies, questioned the implication that “poor people left to their own devices will just wallow in the slums.”

This criticism has been raised before. But the real takeaway, Staiger stressed, is that it’s harmful to wall people off from society.

Moreta, at Old Colony, can already feel the difference. She and her family moved to another public housing complex during the final phase of construction, and came back about a year ago. Her new apartment is spacious, with high ceilings and central air conditioning. Security cameras and key cards make the property more secure.

More than anything, she said, she finally feels like she belongs.

“Everything has changed because the appearance of the buildings has changed,” said Moreta, who works in a high school cafeteria.

Her daughter Brianny, who is finishing up her freshman year, gets straight A’s. Her friends sometimes joke about her being from “the projects,” her mother said, but, so far, she isn’t experiencing the discrimination and stress that Samuel did.

And she’s thinking big. Samuel, now 27, recently told Brianny, who loves to draw, she should think about art school.

“Art school?” she scoffed. “I’m aiming for Harvard.”

This story was produced by the Globe’s Money, Power, Inequality team, which covers the racial wealth gap in Greater Boston. You can sign up for the newsletter here.

Katie Johnston can be reached at katie.johnston@globe.com. Follow her @ktkjohnston.