Nanci Kauffman resigned on Sept. 7 as head of Castilleja School, concluding a 13-year term that was in many ways defined by the school's contentious plan to redevelop its Bryant Street campus.

Kauffman announced her departure three weeks into the start of the new school year in a Sept. 7 letter to the school community.

"Throughout my career as an educator, I have always embraced the unique opportunity for new beginnings that come with the start of the school year. This fall, as I looked toward the paths that lie ahead for Castilleja, I realized it was time to step down and make room for new perspectives," Kauffman wrote. "At this pivotal moment for Castilleja, with so many exciting adventures on the horizon, it is time for new leadership."

A resident of Old Palo Alto, she joined the school as a sixth-grade history teacher in 1999 and ultimately ascended to the top leadership position in the fall of 2010. She referred to Castilleja in the letter as her "element," a word she defined as a "place of joy where your talents meet your passions and where you live your most productive and fulfilling life."

Kauffman could not be reached for comment.

Kathy Layendecker, who has worked as associate head of school for the past six years and as chief financial and operating officer since 2014, will serve as its acting head, the Board of Directors announced.

She will work with the recently retained executive advisor Kathleen O'Neill Jamieson and a soon-to-be assembled Faculty Advisory Council comprising education experts to find an interim head of school, according to a joint statement from board Chair Zac Zeitlin and Vice Chair Odette Harris. That person would lead the school while it conducts a national search for a permanent head.

Zeitlin and Harris credited Kauffman for her role in educating over 1,500 young women who went through Castilleja during her 24 years at the school.

"Rooted in her belief in the power of women's education, Nanci has led with care and compassion through some of the most pivotal academic and social advances in school history," the statement reads.

"During Nanci's tenure, Castilleja has built a reputation for pioneering work in innovation and equity with concepts such as the Bourn Idea Lab and the Ace Center. The school has further strengthened its position as a nationally recognized leader in education."

An education veteran, Kauffman began her career in 1979 as a teacher at Marymount School, a girl's school in New York City. She subsequently served as a history teacher, a tennis coach and dean of faculty, among other positions.

But in the latter half of her term as head of Castilleja, she increasingly found herself in a new role: as the public face of one of the community's most contentious and polarizing development projects.

The Castilleja project, which went through six years of debate and multiple revisions before winning approval in June 2022, involves rebuilding most of the academic buildings and constructing an underground garage.

It also calls for gradually increasing the school's student enrollment — a controversial issue since 2013, when the city learned that the school had been violating its enrollment limit for over a dozen years. The city ordered it to pay a $300,000 fine and to gradually reduce its student population from 448 to the allowed limit of 415. (A decade later, the school still enrolls more than 415 students.)

While the violations began well before Kauffman took over as head of school, they overshadowed Castilleja's modernization plans and severely damaged the school's reputation among its neighbors. A torrent of neighborhood opposition arose to the redevelopment, with critics pointing to the school's checkered history of compliance and lobbying the council to either downsize the project or reject it altogether.

The conflict grew increasingly intense, with project supporters and opponents flocking en masse to public hearings and blanketing the neighborhood with posters advocating for their respective positions.

While project advocates emphasized Castilleja's sterling reputation as an education institution and wore T-shirts that read "When women thrive, all of society benefits," members of the group Protect Neighborhood Quality of Life Now argued that its plans were incompatible with the single-family neighborhood around it.

Some called for Castilleja to build a second campus elsewhere or to leave Palo Alto altogether.

Rob Levitsky, a vocal opponent of the Castilleja project, was among those who framed it as a money grab that tramples over both zoning laws and neighborhood expectations.

"Money is why the school has cheated on enrollment for the last 20 years," Levitsky told the council at a May 2022 meeting, two weeks before the project received its final approval.

In countering these criticisms, Kauffman pointed to the school's recent efforts to reduce traffic and parking impacts. This included an ambitious transportation-demand-management program comprising carpooling, shuttles and limitations on the number of days school staff can drive to work solo.

It will have to redouble these efforts in the coming years thanks to a "no net new trips" requirement that the council included in its approval of Castilleja's redevelopment plan.

"When you consider how dramatically we have reduced our impact on the neighborhood over the last 10 years in terms of reducing trips, reducing events, reducing noise, reducing parking — we feel we have earned our right to be trusted at this point," Kauffman told this publication in an April 2022 interview.

The council's approval allows Castilleja to raise its student enrollment to 450 and creates a path to ultimately get to 540 if the school proves that it can keep its traffic impacts minimal. Kauffman's resignation will not impede the redevelopment plan, Layendecker told this publication.

"The leadership transition does not change Castilleja's long-standing commitment to modernizing our campus," she wrote in an email.

Layendecker also vowed in a letter to the school community that she will keep everyone apprised of developments related to Castilleja's academic and co-curricular programs, as well as the new campus project.

She also said she will "seek input on important decisions" facing the school, which includes partnering with Jamieson and the Faculty Advisory Council.

"I take on this role knowing that I am among outstanding educational professionals who will partner with me in delivering on our mission and providing an outstanding and joyful learning environment for our students," Layendecker wrote.

"I also know I can rely on our strong parent and alumnae communities; both are deeply committed to Castilleja's past, present, and future," she wrote.