When Neil J. McNeill Jr., principal of the Middle School for Art and Philosophy in Brooklyn, learned that fewer than 4 percent of his students had passed state exams in math last year, he was frustrated.
It so happened that he shared a building with one of the top-performing schools in the Brownsville neighborhood, Kings Collegiate Charter School, where 37 percent of the students had passed, well above the New York City middle-school average of 27 percent.
Mr. McNeill had long been curious about the charter school’s strategies: It, too, served large numbers of low-income black students, many from the same neighborhoods. But the two schools operated in their own bubbles, with separate public-address systems and different textbooks. And as a matter of practice, they did not talk about academics.
“We are kind of two ships in the night,” Mr. McNeill, 39, said recently.
A primary rationale for the creation of charter schools, which are publicly financed and privately run, was to develop test kitchens for practices that could be exported into the traditional schools. President Obama, in recently proclaiming “National Charter Schools Week,” said they “can provide effective approaches for the broader public education system.”
But two decades since the schools began to appear, educators from both systems concede that very little of what has worked for charter schools has found its way into regular classrooms. Testy political battles over space and money, including one that became glaringly public in New York State this spring, have inhibited attempts at collaboration. The sharing of school buildings, which in theory should foster communication, has more frequently led to conflict.
And some charter schools have veered so sharply from the traditional model — with longer school years, armies of nonunion workers and flashy enrichment opportunities like trips to the Galápagos Islands — that their ideas are viewed as unworkable in regular schools.
In recent years, educational leaders, concerned about hostilities between the two types of schools, have worked to encourage warmer relations. In Tulsa, Okla., charter schools and district schools are working together to improve teaching quality. And in Spring Branch, Tex., charter school leaders are helping train district teachers and principals.
The Bill and Melinda Gates Foundation has helped finance some of those efforts,offering $25 million in grants over the past several years for educators interested in tackling common problems.
In New York City, Mayor Bill de Blasio has promised a new era of collaboration after months of sparring with charter school leaders. The new contract the city and the teachers’ union agreed to this month gives educators in some schools the latitude to change work rules, in hopes of creating charterlike conditions.
“The spreading of ideas and innovation clearly has been a very imperfect process,” Mr. de Blasio said this month in a radio interview. “What we’ve seen in too many cases is charters and traditional public schools disconnected rather than being mutually involved for innovation.”
Mr. de Blasio also recently began a program to encourage schools across the system to share best practices.
Even so, charter schools were not included in the initial group.
Education experts said it might prove difficult to encourage the kind of sharing of ideas that charter schools were originally supposed to foster, given competitive dynamics. Charter schools serve about 5 percent of public-school students nationwide, according to the National Alliance for Public Charter Schools, up from about 1 percent in 2003. In some cities, like Detroit, New Orleans and Washington, the percentages are much higher. (In New York, it is 6 percent.)
“It’s like putting a Burger King kitty-corner to a McDonald’s and expecting — in the same location and competing for the same families — warm and fuzzy cooperation,” said Bruce Fuller, a professor of education and public policy at the University of California, Berkeley.
Charter schools are known for aggressive recruiting campaigns, and at schools with dwindling enrollment, every student counts: In New York, each brings more than $10,000 in education financing.
Michael Mulgrew, president of the United Federation of Teachers in New York, said competition made partnerships unrealistic. “It’s like ‘The Hunger Games,’ ” he said.
The first charter schools in the United States opened in the early 1990s, and were popular among advocates interested in radically overhauling the traditional model of schooling. The schools were given freedom from regulations about staffing, curriculum and scheduling in hopes that they could devise superior models.
As their numbers grew rapidly over the past decade, tensions worsened in many cities. Labor groups have emerged as some of the most vehement critics of charter schools, which are typically not unionized, depriving them of members.
This spring, a battle broke out in New York State as charter advocates pushed for access to free classroom space. They spent millions of dollars on television advertisements, and with the help of Gov. Andrew M. Cuomo, won some of the most generous protections in the country.
Charter school leaders have defended their efforts, pointing to strong academic results in some of the poorest neighborhoods. But some also say that the tactics of the movement are partly to blame for the reluctance of district leaders to work with them.
“I got into this to create R&D for regular schools,” said Steve Barr, founder of Green Dot Public Schools, which operates charter schools in Los Angeles. “But sometimes we come off as if we’ve invented everything.”
Despite the backlash, some school districts have adopted practices embraced by charter schools, including longer school days, smaller high schools and more autonomy for principals.
In New York, the Gates Foundation, state and city education officials, and charter school leaders have worked to reduce friction. Charter schools often share classroom space, cafeterias and gyms with traditional public schools, which has created hostility within some buildings.
The Bronx Charter School for Excellence and the nearby Public School 85 are exceptions. Since winning a state grant in 2013, the schools have worked together to improve the quality of their kindergarten programs. They have held teacher exchanges, and every week they come together to discuss topics like student participation and reading strategies.
At first, staff members on both sides seemed dubious, and sat on different sides of the room.
“There was this idea that we were trying to turn this school into the charter, this grand conspiracy of, ‘Oh my God, are we going to be taken over, are we going to be closed?’ ” said Charlene Reid, head of the Bronx Charter School for Excellence.
But now, staff members said they shared observations and ideas by email several times per day. As a result, P.S. 85 began assessing student reading levels earlier in the year and increased the rigor of reading assignments.
In Brooklyn, the Middle School for Art and Philosophy and Kings Collegiate Charter School, which have been neighbors for seven years, have started talking about how they might collaborate.
Mr. McNeill said there were aspects of the charter school that appealed to him, including its smaller class sizes and aggressive outreach to parents. But he said that despite the school’s test scores, it would be a mistake to assume it had all the solutions.
The school serves a much smaller percentage of students with disabilities, for example. And some of its practices, such as a strict code of discipline, might be difficult to put in place in a traditional public school.
Mr. McNeill said the schools would have to work to overcome tensions between some charter school families and those who attend the traditional program. Still, he said, more collaboration was important, pointing to a mural at the entrance of the school, which depicts a handshake, a symbol of solidarity between the two schools.
“There’s no reason why there shouldn’t be that type of cooperation and collegiality,” he said. “It will give our kids an opportunity to show they are certainly no different from the kids upstairs, that they have the same promise and the same potential.”