After a weeks-long and emotionally charged process to establish new attendance zones for middle and high schools in eastern Loudoun, the county School Board voted Tuesday to adopt a plan that will reassign thousands of students to new schools in the Ashburn and Dulles North area.

The new boundaries were needed to accommodate the opening of three new schools. Trailside Middle School and an unnamed high school, HS-6, will open in fall 2014. A second unnamed high school, HS-8, is scheduled to open in fall 2015.

The School Board, which had been considering seven plans, ultimately supported an amended version of Plan 12, which reassigns much of the Brambleton community from Briar Woods High School to HS-6.

At recent public hearings that drew hundreds of residents to the school administration building’s board meeting room in Ashburn, scores of parents from the Brambleton and Broadlands communities were among the most impassioned speakers. They repeatedly urged the School Board to keep their students at Briar Woods. The high school is operating well beyond its capacity and is using 10 classroom trailers to accommodate students.

As expected, the board’s vote angered many Brambleton families, some of which have refused to accept the outcome. Resident Richard Kelsey, assistant dean for management and planning at George Mason University School of Law, said this week that community members are considering legal action.

The School Board was notified Wednesday that litigation is “likely,” Kelsey said, and board members were instructed to preserve any relevant records and communications.

“Residents of Brambleton believe the school boundary process was both improper and essentially predetermined,” Kelsey said in an e-mail Thursday. “They believe that board members failed to consider the law.”

Lawyers are evaluating Brambleton’s legal avenues, he said.

An attempt at legal recourse could mark the third time in recent memory that an attendance zone dispute has moved into a courtroom. In January 2012, residents of two Leesburg communities filed separate petitions for judicial review after the School Board voted to adopt new boundaries for Leesburg elementary schools. In both cases, Loudoun Circuit Court Judge Thomas D. Horne ruled in favor of the board.

Of the plans considered, the adopted map results in the lowest number of relocated students. If the boundaries were to go into effect today, about 4,000 students would be reassigned, schools officials said. The plan also maintains direct feeds across the area, meaning that students will stay together as they move from middle school to high school, officials said.

At Tuesday’s meeting, School Board members said they are hopeful that the new plan will guard against future rezoning in neighborhoods that have been through the reassignment process numerous times. By organizing the map around communities that are mostly built out, including Broadlands, Ashburn Village and Ashburn Farm, the new assignments are more likely to last, some board members said.

It was this scenario that led the board to support moving Brambleton to HS-6. Board member Jeff Morse noted that because Brambleton is still a fast-growing community, it will quickly outgrow Briar Woods.

“We have to realize Brambleton is going to be the largest HOA in Loudoun County. It will never ever fit back into one high school when it grows and grows and grows,” Morse said. He added that other built-out communities had been moved multiple times and deserved some measure of permanence. “Those communities can achieve a level of stability that we cannot achieve in a growing community,” he said.

The board voted, 7 to 2, to support Plan 12, originally drafted by Morse and fellow board member Kevin Kuesters (Broad Run). School Board Vice President Jill Turgeon (Blue Ridge) and member Thomas E. Reed (Leesburg) did not support the plan.

Reed contested the notion that the plan would protect against future reassignments for more established communities in Ashburn.

“Ashburn stability is an oxymoron. We are going to have growth in this area for the next decade,” he said. “All these areas are going to have to be redone.”

School Board member Brenda Sheridan (Sterling) said that although she reservations about Plan 12, it is important for school leaders and community members to accept it.

“We knew that there wasn’t going to be a plan that makes everybody happy. There is no perfect plan,” she said. “I don’t think obviously it’s going to make Brambleton happy, and I feel badly for them, but at the same time, I think it’s important for us to embrace a new plan.”

School Board Chairman Eric Hornberger (Ashburn) reiterated that the adopted plan would offer the best chance at lasting consistency.

“We all know that this has been a difficult process and a painful path in many ways,” he said. “The good news is that what we have in front of us should provide us stability. At long last, the stability that we crave.”

Echoing comments made by his colleagues, Hornberger said a solution that would have pleased everyone was never a possibility.

“There is no silver bullet, no matter how many times we try to find one,” he said.