A new science-themed D.C. charter school plans to open its doors this fall across the street from a traditional school that serves the same grade levels and has the same academic focus, highlighting a lack of coordination that has drawn increasing scrutiny in recent months.

As charter schools flourish, they often are competing with neighborhood schools for the city’s students, and the two sectors barely communicate about their plans. The move by Harmony School of Excellence-D.C. into a building across the street from Langley Elementary came as a surprise even to Schools Chancellor Kaya Henderson, who learned about it on Twitter.

Henderson called Harmony’s move an inefficient use of tax­payer dollars and a sign of a choice that the city is going to have to make: Does the District want to plan for the coexistence of charter schools alongside a system of traditional neighborhood schools? Or does the city want to continue with a laissez-faire approach that Henderson said could give rise to a “cannibalistic environment” in which “somebody gets eaten”?

“Either we want neighborhood schools or we want cannibalism, but you can’t have both,” Henderson said, adding her voice to a growing chorus of people who have called for joint planning between traditional and charter schools and perhaps a limit on the number of independent charter schools in the District.

“A citywide conversation about how many schools do we need, and how do we get to the right number of schools, as opposed to continuing to allow as many schools to proliferate as possible, is probably a necessary conversation to have at some point,” Henderson said.

Charter schools do not have to specify or propose a location when they apply to the D.C. Public Charter School Board for approval. The board considers applications on their merits, without taking into account the impact on existing schools; once a school is approved, it goes about finding a home, and then must notify the board of its location before opening its doors to students.

Charter board officials and advocates have long argued that location can’t be a factor in school approvals because real estate is so hard to find that schools often don’t have much choice.

Officials with Harmony, a ­Texas-based chain that specializes in science, technology, engineering and math (STEM) education, said they conducted an extensive search and found just one workable place for their new elementary school: an old parochial school building on T Street Northeast, in the city’s fast-gentrifying Bloomingdale neighborhood.

The building is directly across the street from Langley, another STEM-focused elementary that was recently renovated and that has been working to build interest among young families living nearby.

Soner Tarim, superintendent of the Harmony charter network, said he hadn’t realized that Langley was a STEM school. He said that the dearth of other options led him to sign a lease for the building, and he believes that — because charter schools enroll students from across the city — most of Harmony’s students will come from outside of Langley’s attendance zone and outside of Ward 5.

“I’ve never spent this much time during my 14 years of charter schooling” on securing real estate, Tarim said. “This was the most intense search.”

Also across the street from Harmony are the recently renovated McKinley Tech middle and high schools, both of which are STEM-focused. Tarim eventually plans to expand Harmony into a K-12 STEM school, but he said older grades will have to be placed elsewhere because the building is too small to accommodate them.

The issue of joint planning has attracted more attention in recent months amid the push to overhaul traditional public school boundaries for the first time in four decades. Parents and politicians have questioned how the District can redraw school maps — and thoughtfully plan for the future — without considering charter schools, which enroll nearly half of the city’s schoolchildren.

The advisory committee overseeing the boundary overhaul has recommended that the District address the lack of coordination between the two sectors, but — facing resistance from charter advocates — stopped short of making specific recommendations.

Charter advocates say the District could help guide charters’ locations by releasing some of the many surplus school buildings that sit empty, and they said they were open to sharing more information with the school system.

But they are firmly opposed to ceding their independence to government officials in the name of joint planning.

“Yes, there is room for better communication and information-sharing as each sector — DCPS and charter schools — makes decisions,” Scott Pearson, the charter board’s executive director, wrote in a Washington Post letter to the editor in May. “But protecting a traditional school is no reason to keep a great charter school from opening its doors.”

A charter board spokeswoman said Pearson was not available for an interview for this article, but she pointed to a May board meeting during which Pearson said he is encouraging newly approved schools to meet with the city’s deputy mayor of education to describe their facilities plans.

Henderson said that she envisions a process that would allow city and charter board officials to identify which neighborhoods most need new, good schools and which neighborhoods would benefit from specialty programs. The charter board would then use those priorities in determining which new schools should be approved, she said.

“The citizens deserve better, with the dollars that they entrust us with, than this random, haphazard stuff,” Henderson said. “I think this mayor, this deputy mayor, myself, we all support charter schools . . . but I don’t think anybody signed up for the kind of uncontrolled expansion of schools, without rhyme or reason.”

Ramona Edelin, executive director of the D.C. Association of Chartered Public Schools, said it is not surprising that the chancellor of the traditional school system would want a say in which charters are approved and where they’re allowed to open.

But “nobody outside the charter school sector should have a veto power over where our schools locate,” Edelin said. “Charter schools are autonomous and free from that kind of control from the government, and that’s a requirement of their success.”

Responding to Henderson’s characterization that charters are cannibalizing the school system, Edelin said that “competition should be good for the neighborhood.”

The school system’s struggles to maintain enrollment are “not just because there’s a charter school nearby,” she said. “It’s because they’re seen as better, and parents are voting with their feet.”