Barry Fried, the longtime principal of John Dewey High School, was removed from the Brooklyn school suddenly this morning, according to several teachers at the school.

It was not immediately clear whether Fried’s removal was related to “turnaround,” the federally prescribed reform process that the city has proposed for Dewey and 32 other struggling schools. Turnaround requires principals who have been in place for more than a few years to be replaced, and the city has started informing principals at some of the schools that they would be removed at the end of the year.

But Fried’s departure happened abruptly, suggesting that the city might have had more immediate concerns. Department of Education officials did not respond to requests for details about Fried’s departure today.

At a faculty meeting this afternoon, Kathleen Elvin was introduced as the school’s interim acting principal. Elvin was the founding principal of a successful small high school, Williamsburg Prep, and most recently trained teachers assigned to schools undergoing less agressive overhaul strategies. She is likely to help engineer staffing and programming changes at the school through the turnaround process.

The change, according to people familiar with the school, was sorely needed — but comes after too long with subpar leadership.

“Principal Fried sits in his office all day and can’t control the students,” City Councilman Dominic Recchia, a 1977 Dewey graduate, said at a public meeting earlier this year, according to the Brooklyn Daily. “This principal should have been gone years ago. The school could prosper but it needs new leadership.”

Under Fried’s tenure, Dewey — which was founded in 1969 as a “modern” school with progressive instruction — earned solidly mediocre scores on the city’s progress reports and saw a spike in violent incidents. After a lockdown in 2008 when a student was seen with a gun in a classroom, the open campus was closed and students could no longer leave during the day.

When the city assigned dozens of schools to “transformation” in 2010, requiring the removal of longtime principals, it left Dewey untouched and Fried in place. In 2011, Fried stayed on after the city assigned Dewey a nonprofit partner through “restart.”

“In 2010 if Dewey got the transformation model, we would’ve gotten a new principal who could’ve helped the school,” said a teacher who has worked at the school since before Fried arrived in 1997. “The DOE clearly didn’t give Dewey a chance by keeping Fried in the school.”

Today, Leo Casey, the UFT vice president in charge of high schools, said Fried was a poor leader, but the city was making matters worse by removing Fried in the middle of the year.”There were longstanding issues concerning his ability to lead the school, but despite acknowledging that, the DOE did nothing to find a replacement,” Casey said. “Now, they are doing it in the middle of the term, which is disruptive, because it suits their organizational purposes to do so.”

Teachers and students at the school have been vigorously protesting the turnaround plan, holding weekly rallies outside the school. Last Friday, Dewey students walked out of classes in protest, and on Monday they turned out en masse for a meeting about turnaround held at Brooklyn Borough Hall.