Things can get complicated when a school’s landlord is its main competitor.

Just ask families at GEE Edmonson, a Detroit charter school renting a building owned by the city’s main school district. The district announced in February that it would be taking the building back to turn it into a district Montessori program.

Three other charter schools have been told the same: Your lease is up.

“She’s very upset by it,” Evette Napier said of her daughter, a sixth-grader at GEE Edmonson, who won’t be able to stay in the building after it is reclaimed by the district because the new school will only go up to third grade. “All of her friends, they’ve been together since kindergarten, and they don’t want to be separated. But they don’t know what school their parents are going to put them in.”

Detroit Superintendent Nikolai Vitti says he is addressing a problem specific to his city by undoing a misbegotten plan by state-appointed emergency managers to turn district schools into charters.

But it’s also a stark illustration of the risks charter schools face across the country when they depend on districts for something as crucial to their operations as space. Leasing district property can leave schools with little recourse when new district leaders decide, like Vitti did in Detroit, that there are better uses for their buildings, something that seems increasingly likely as support for charters ebbs in some cities.

“We’re in the midst of some turbulent waters,” said Todd Ziebarth, a vice president at the National Alliance for Public Charter Schools. “If I was running a charter school that was in a district facility or that was authorized by a district, I would make sure that there was a plan B or C in place.”

That may be easier said than done.

Leaders of one New Mexico charter school are gearing up for a court battle against the Santa Fe district after the district announced plans to move the school out of its current building and to a different site. Parents at a charter school in Phoenix, Arizona were furious last year after the city district hit the school with a massive rent hike. And charters in Oklahoma City and Ventura County, California are being forced to move to different buildings as part of local districts’ restructuring plans.

This sort of uncertainty will be familiar to anyone who has rented property, but it was practically unheard of in American public education before the charter school movement picked up steam in the 1990s. Traditional districts typically pay for buildings using cheap, long-term, state-backed bonds.

Corruption is one infamous result of charters’ reliance on rented buildings. Investigations from California to Michigan to New Jersey have documented self-dealing lease agreements that allow charter operators to pocket government funds.

Less examined is the uncertainty that students and families face when schools operate in buildings they don’t control.

Today, more than 1 in 5 charters rent facilities from traditional districts. They serve only a small portion of U.S. public school students — the total number enrolled in charters is about 6 percent — but this arrangement can have a broad impact in cities with large charter sectors.

And it can feel especially precarious in cities where districts and charter schools compete fiercely for a limited number of students, as they do in many Detroit neighborhoods. A decision that pushes a school to move or close could add to the already crushing instability facing many families, who often hop from one school to another in search of an elusive high-quality option.

Others note that charters know what they’re getting into — and have long benefited from using district buildings while also recruiting the district’s students. “They’re undermining the public school system,” said Gary Miron, an education professor at Western Michigan University. Rather than give charters easier access to school buildings, as some have sought to do, Miron said, “the better tactic would be a moratorium on charters.”

In the 1990s, when nearly every U.S. state created laws to allow charter schools, few set aside any funds for charter school facilities, and few provisions were put in place to shape the way charters and districts share space.

In recent years, though, charter advocates have successfully passed dozens of state laws requiring districts to share facilities with charters. That’s what happened in New York City: After the charter-friendly mayor Michael Bloomberg was succeeded by the charter-skeptical Bill de Blasio, state lawmakers passed a law requiring the city to provide public space or pay for space elsewhere for new or growing charter schools. In Indiana, school districts are required to offer vacant district buildings to charter schools for $1.

But “districts remain the decision makers” in most places, according to a 2017 report on charter school facilities from the Center on Reinventing Public Education, a think tank focused on school choice.

In Detroit, Vitti’s move to end the district’s leases with several charters was largely met with a shrug from the charter leaders, who said the decision was clearly communicated in advance — and even that they could sympathize with his competitive instinct.

Vitti himself has framed the decision as a corrective. He argues that district school buildings were handed to charters haphazardly, including in neighborhoods that don’t have another district school.

“At this juncture, it’s about trying to make up for what didn’t happen in the past,” Vitti said.

Still, some see politics undergirding Vitti’s actions, too.

“There’s been a partisan shift at the top of the state,” said LaMar Lemmons, a former member of the Detroit school board. “[Vitti] knows they aren’t going to be attacked from the governor’s office, the state board of education, and the attorney general, all of which were used against the district in the previous administration.”

In the cities that appear most stable for charters that occupy district buildings, charter advocates often control the school boards. That’s the situation in Indianapolis, where numerous charter schools lease district buildings with little friction.

Earl Phalen, a charter operator with schools in Detroit and Indianapolis, understands better than most the risks of sharing district space. Vitti ended the leases of his three schools in Detroit last year.

Unable to find new buildings, Phalen’s schools consolidated into one. Hundreds of families had to change schools as a result.

“Unfortunately, in some regions, districts may see charters as a threat or as competition,” Phalen said in an emailed statement. “When that is the case — no one wins.”

Yet Vitti is not known for unconditional animosity to charter schools. He has said he thinks it’s possible that the Detroit district could eventually work with some charter schools, and he collaborated with charters in previous jobs.

The fact remains, though, that in Detroit and many other cities, districts and charters are competitors for a shrinking pool of students.

“You have to maximize the buildings that you have,” Vitti said.