File: Wilson High School Principal Pete Cahall (Nikki Kahn/The Washington Post)

Peter Cahall, the Wilson High School principal who made national headlines last year when he came out as gay to his students at Pride Day activities, said he learned this month that his contract will not be renewed next school year because of test-score performance at the Northwest Washington school.

He notified parents and students of his impending departure in an e-mail late Friday afternoon.

“I [am] determined to finish this school year with as much passion, energy and commitment that I have invested in the last six,” Cahall wrote. “I have transitioned through the five stages of grief. . . . Denial, Anger, Bargaining, Depression, and Acceptance. I am at the acceptance stage.”

In an interview, Cahall said he had not intended to make a contentious exit. But in a letter to the D.C. Council that Washington City Paper first published Friday afternoon, Cahall called the decision “arbitrary and capricious” and criticized the system’s adversarial relationship with school leaders.

“I wish you well in moving the school system forward and want nothing more than for DCPS to be successful,” Cahall wrote. “Unfortunately, when you have this type of adversarial relationship with the leaders of the schools, I do not believe that success is possible.”

D.C. principals work under one-year contracts, and they are evaluated annually on six criteria: instruction, talent, school culture, operations, family and community, and personal leadership. The process means that principals must demonstrate their worth each year, and it yields a wave of annual departures. That turnover has prompted ongoing public debate about leadership instability in the city’s schools.

Wilson is by far the city’s largest comprehensive public high school, with more than 1,700 students. It is located in Ward 3, the most affluent part of the District, but it serves a wider and more diverse population racially and socioeconomically.

Former schools chancellor Michelle Rhee hired Cahall, a former Montgomery County school administrator, in 2008. Parents credit him with helping to bring more order and efficiency to the crowded school, and he oversaw a top-to-bottom renovation of the school in 2010.

During his tenure, Wilson has boasted one of the city’s highest numbers of Advanced Placement offerings and a graduation rate well above the city average.

D.C. Council member Mary Cheh (Ward 3) said that Cahall has been “highly regarded” and “well respected” by parents and that she was “somewhat skeptical of the basis” for his termination.

“If you look at the whole course of his record and the esteem in which he’s held, I think it’s somewhat of a surprise. I would be interested to know how it’s warranted,” she said.

Cahall said in the letter that he was told that he is losing his job because “I have not moved the school forward academically based on the DCCAS scores.”

Wilson is classified as a “focus school,” the second-lowest of five tiers on a rating system used for federal accountability purposes. According to the DCPS Web site, the designation means that the school needs “targeted support” to address achievement gaps in testing performance between groups of students.

The school has posted significant disparities over time in math and reading proficiency rates for white and African American students. In the 2011-2012 and 2012-2013 school years, more than 90 percent of white students were proficient or advanced on city exams, while proficiency rates hovered between 45 and 50 percent for African American students.

But last school year, African Americans saw a double-digit increase in performance, to 59 percent proficiency in math and 62 percent proficiency in reading.

In his letter to the council, Cahall included the recent test-score gains as an example of his accomplishments during the past six years. He also cited his leadership during a $120 million modernization that involved a one-year move off campus, as well as increases in the number of Advanced Placement exams students have taken and passed.

Terry Lynch, a parent and school activist, said Cahall was under “enormous pressure” given how crowded the school is and how it’s compared with selective schools or charter schools that are able to restrict enrollment or admissions in different ways.

“You have a principal . . . who is expected to achieve miracles,” he said.