Castilleja School will be able to reconstruct its Bryant Street campus and increase enrollment after the Palo Alto City Council voted Monday to approve the school's contentious plan after six years of bitter debate.

The council voted 6-1, with Vice Mayor Lydia Kou dissenting, to approve what for years has been the most complex and fiercely debated proposal in the city's development pipeline. The project — which includes reconstructing the academic buildings at the all-girls school, building an underground garage and gradually increasing student enrollment — had already gone through 22 public hearings, various design revisions and two separate approval processes involving the Planning and Transportation Commission and the Architectural Review Board.

The Monday vote represents a hard-fought — if conditional — victory for Castilleja. Once it completes construction on the new buildings, it will be allowed to immediately raise its enrollment from the current level of 422 to 450. While that is well shy of the 540 that Castilleja had requested in its conditional use permit application, the council's approval creates a path for getting to that higher level. It would require Castilleja to create an aggressive transportation-demand management plan that keeps traffic at its current levels. It would also require the school to prohibit juniors from driving and to ensure that at least 40% of its student population lives within 5 miles of the Castilleja's campus at 1310 Bryant St.

In approving the project, council members repeatedly alluded to its tortuous and acrimonious journey through the planning process. Opponents of the project often cited the school's history of failing to abide with the enrollment cap in its existing conditional use permit, a violation that prompted the city to issue a $265,000 fine against Castilleja in 2013 and to demand a gradual reduction in enrollment. They had also argued that the reconstruction project runs afoul of zoning rules and that Castilleja's proposed underground garage is out of place in the single-family neighborhood.

Council member Greer Stone characterized the council's approval of the project, which gives Castilleja most of what it asked for but attaches new conditions to ensure its impacts on the neighborhood are contained, as a compromise between the school and its critics.

"There has been a breakdown in trust and I think both sides recognize that," Stone said. "This motion allows that trust to hopefully be rebuilt.

"It will allow Castilleja to ultimately get to 540 but will provide neighbors and residents the ability to have a seat at the table, to have a voice and actually have some power to work with the city to be able to provide that feedback."

For the council, the Monday hearing was the second meeting in two weeks focused on the Castilleja project. On May 23, council members heard from dozens of residents representing both sides of the debate, with opponents characterizing Castilleja's proposal as an aggressive overreach in a single-family residential zone and supporters suggesting that the project would represent an improvement to both the school and the neighborhood while also furthering the mission of supporting education for young women.

The council's vote comported in some respects the recommendations of the Planning and Transportation Commission, which voted in favor of lowering both the number of annual events and the maximum enrollment figure. The commission's majority took a position in April that Castilleja should prove that can expand student population without adding car trips before it could request an enrollment increase beyond 450. The council also agreed to sign a joint statement with the school stating its intention to ultimately set the limit at 540.

But in a concession to the school's critics, the council also agreed to reduce the number events that Castilleja would be allowed to hold every year. While the school has historically held more than 90 special events — those with 50 or more attendees — per year, its proposed conditional use permit would have lowered the number to 70, while also allowing five "major events" with 500 or more participants. The council lowered the number to 50 special events and five major events, consistent with the recommendation of the planning commission.

The council also added several new conditions to appease residents' concerns about the proposed traffic and parking impacts of the enrollment increases. Mayor Pat Burt proposed banning juniors from driving to the school, a condition that his colleagues supported. The new rule will allow five exemptions for special circumstances, such as when students don't have access to public transportation or to school shuttles.

"I think with bicycles and particularly e-bicycles, there's no reason why a student within 5 miles or so shouldn't be able to bike to school," Burt said.

Burt also successfully advocated for requiring Castilleja to ensure that at least 40% of its students live within 5 miles of the campus, a move designed to both increase the school's benefit to the local community and to mitigate its traffic impacts.

Another condition, which was pitched by council member Tom DuBois, would create a three-person committee of neighborhood residents that will review Castilleja's transportation-demand programs and help determine whether the school's traffic-reduction programs warrant changes in enrollment levels or the number of authorized events.

Supporters of Castilleja, many of whom have expressed frustrations in the past about the council's failure to advance the project, cheered the council's Monday decision. Nanci Kauffman, head of school at Castilleja, she is grateful to the council for its work in advancing the project.

"I am ecstatic that we are going to be able to enroll more students," Kauffman told the Weekly after the hearing. "This is about the future of the school."

Kauffman said the council's decision will enable Castilleja to stay in Palo Alto, to remain financially viable and to educate more girls.

"We knew there would be a lot of conditions and we are prepared to do what we need to do," she said.

Others were less thrilled. Members of the group Preserve Neighborhood Quality of Life Now said they were disappointed about some of the conditions in the approval. The council has agreed, for example, to allow Castilleja to use its existing traffic consultant to verify its traffic volumes rather than requiring an affirmation from independent consultant. Andie Reed, founder of PNQL Now, said this is a problem. The council, she said, deferred too much in Castilleja's attorney in crafting the conditions around transportation-demand management (TDM), which are key to its enrollment plan.

"It's all about the TDM and whether they can get enrollment increases based on that," Reed said. "You can't use the school's traffic consultant."

She also suggested that the council should have simply set the number of special events at 50 per year without creating an avenue for increasing this number through a recommendation from the new neighborhood committee. But Hank Sousa, also a member of the neighborhood group, called the council's prohibition on juniors driving a "modest victory" and took some solace in the fact that the enrollment levels will not exceed 450 for a while.

Council members also disagreed about numerous components of the project, even as they ultimately coalesced toward approval. Council member Alison Cormack urged her colleagues not to reduce the number of special events that Castilleja is allowed to hold. Her proposal to raise the number from 50 to 70 failed to win support from her colleagues.

"My concern is that we're arbitrarily removing opportunities for students and their families to participate in important events," Cormack said.

Kou, meanwhile, had broader concerns about the project and said she could not make the necessary findings that are needed to approve the variance that Castilleja requires to build the new academic buildings once the existing ones are demolished.

"There's just no way to make the findings on this and I'm kind of perturbed that we're approving the variance that we can't find the findings on," Kou said.

But despite some reservations, her colleagues agreed that it's time to approve the project. Council member Eric Filseth suggested that the proposal that the council ended up with strikes the right balance when it comes to enrollment and supported the formation of a committee that would review Castilleja's compliance with its conditions of approval and make recommendations to the planning director.

"I think if someone came to us and said, 'I just acquired this many acres in the middle of Old Palo Alto and I want to put a school there,' we'd probably turn them down," Filseth said. "But the reality is that this is not the situation here. Castilleja has been in the community for a century or more. There's a lot of people in town who use it and like it and we are an education town, not just a public education town."