The leader of a New Orleans charter high school that is under investigation for allegedly cheating on state exams has been placed on paid administrative leave.

L.B. Landry-O. Perry Walker High Principal Mary Laurie, who has been widely hailed as a school turnaround specialist, and three of her colleagues have been suspended, effective immediately, according to the charter group that manages the school.

Others placed on leave are Assistant Principals Taisha Williams-Payne and Brian Gibson, and teacher and former test coordinator Trayvonia Duhe.

The move comes a month after the board of the Algiers Charter School Association fired Adrian Morgan, the chief executive officer who alerted the board to the potential impropriety, but at that time left Laurie in place.

It also follows revelations that the school was under a state Inspector General’s Office investigation for its impressive 2013-14 test results, which plummeted the following year after monitors kept a close watch on classrooms.

“ACSA takes allegations of testing impropriety seriously,” the charter group said Monday, adding that it launched its own investigation shortly after the cheating allegations arose and that it has instituted preventative measures to “preserve the integrity of Landry-Walker’s testing and educational environment.”

That internal investigation — along with those by the state and the IG — is ongoing, officials said. Board Chairman John Edwards told earlier this month that the group’s initial probe was inconclusive.

Suspicions arose after Landry-Walker, the product of two high schools that merged in 2013, posted geometry test scores that year that were better than either the former O. Perry Walker High or L.B. Landry High had achieved alone. The scores also were better than those of the longtime high-achieving Lusher Charter School, which selects its students.

The following year, after association officials and the state put more monitors in classrooms, geometry and biology test scores plunged. Four months after those scores were made public, the organization fired Morgan and hired former Principal Rene Lewis-Carter to replace him on an interim basis.

Taking action against Laurie and others was “one of the most difficult things I have ever done,” Lewis-Carter said Monday. Still, she added, “the alleged testing improprieties occurred under their leadership.”

The move was a surprise to Laurie, said her attorney, Willie Zanders. He called it “premature” and “unprofessional.”

“I believe that Ms. Laurie will take the necessary steps to clear her good name,” he said.

Gibson and Duhe did not immediately return calls Monday. Williams-Payne, reached by phone, said she had no comment.

It’s not clear how long the four will be suspended or who will take the reins at Landry-Walker, though association officials said they will announce an interim principal soon.

“Our top priority remains ensuring a safe and rich learning environment for all Landry-Walker High School students,” Lewis-Carter said.

Follow Jessica Williams on Twitter, @jwilliamsNOLA.