Kathleen Grimm, the deputy chancellor for operations and a fixture in the Department of Education under four chancellors, is stepping down, Chancellor Carmen Fariña announced Wednesday.

Grimm oversaw a sprawling portion of the department, including the offices overseeing safety, school support, school food, athletics, space planning, enrollment, human resources, and construction. The only official to have remained in a top post at Tweed since the beginning of the Bloomberg era, Grimm saw her responsibilities expand even further under Fariña, who moved some offices under Grimm when she shrunk the department’s cabinet.

“It is with deep personal regret that I announce a leave pending retirement of Deputy Chancellor Kathleen Grimm, an esteemed colleague who has worked tirelessly to create safe, nurturing environments in which all of our students can learn and thrive,” Fariña said in an email to department staff members.

Grimm, a tax lawyer, was brought on in 2002 for her budgeting and finance expertise and experience in navigating city and state bureaucracy. She had previously served in the state comptroller’s office and the city finance department.

Over her 14-year career at the Department of Education, Grimm preferred to stay behind the scenes, but was thrust into the spotlight when changes to school bus routes, budget cuts, and space planning made headlines.

Her oversight of the city’s transportation of students meant she faced fierce criticism when repeated changes to bus routes angered parents and City Council members. Her oversight of the capital budget and the Blue Book, which sets guidelines for school space use, also made her a frequent target of class-size reduction advocates, who often said the city’s calculations did not reflect reality.

But Grimm was revered within the department for her calm under pressure. She frequently defended the school system in front of the City Council, bearing the brunt of then-education committee chair Eva Moskowitz’s relentless criticism of the city’s toilet-paper offerings in 2004 and, more recently, testifying at hearings on toxic lighting fixtures and school overcrowding.

“Cool and effective, Kathleen stayed for the full twelve years of the Bloomberg administration and did a tough, unglamorous job with distinction,” Klein wrote of Grimm in his memoir “Lessons of Hope.”

On Wednesday, Fariña offered her own praise. “As a senior member of my leadership team, Deputy Chancellor Grimm has provided a strong foundation for our most critical initiatives, including Pre-K for All, Community Schools, and our expanded school support and safety services,” she said.

Grimm’s chief of staff Elizabeth Rose will take over as interim acting deputy chancellor during a search for Grimm’s replacement, Fariña said.