RIVERVIEW — Isaac Anderson didn’t know he was not supposed to leave test answers on the walls of his social studies classroom.

That’s what the 40-year-old teacher told Hillsborough County School District officials when they were called to review his students’ surprisingly high test scores. Shortly before they got his name on a resignation form, he said he thought test security rules were for state exams, not those given by the district.

Anderson’s departure from Spoto High coincides with a larger examination of the school, hailed this past year as a success because of its fast-rising graduation rates.

Investigations into Anderson and former principal Glennis Perez were launched in January and February, not long after superintendent Jeff Eakins staged a Thursday afternoon hot dog party at Spoto to celebrate the latest graduation numbers. All of the district’s principals were invited.

Hillsborough is on its way to achieving Eakins’ goal of a 90 percent graduation rate by 2020, a rapid improvement from rates in the mid-70s just a few years ago. That day at Spoto, Eakins praised school leaders for creating opportunities for students with disabilities and interrupting the cycle of multi-generational poverty. “It’s unprecedented, I hope you know that,” he told the crowd.

To earn a diploma, students must pass state competency tests in math and English or take alternative tests in their place. They must complete a sufficient number of credits. And they must maintain at least a 2.0 grade point average — an area where a teacher who helps students pass their tests can impact a school’s overall performance numbers, including the graduation rate.

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Anderson resigned his teaching position in April. Perez left the school, but not the district, shortly after investigators began focusing on her. She is now an “administrator on special assignment,” according to Yinka Alege, a district deputy director who supervises Spoto and other struggling schools that fall under Hillsborough’s Achievement Schools initiative.

A new principal, Jazrick Haggins, took over at Spoto in May.

Both Anderson and Perez worked together previously at Brandon High, where Perez was an assistant principal.

Their new school had earned C grades from the state for years, and was uncomfortably close to a D.

Glennis Perez, the former principal at Spoto High, has been removed from the school and designated an "administrator on special assignment" while the school district conducts an investigation. Details of the investigation were unavailable. [Hillsborough County Schools]

By the time they arrived, Spoto’s graduation rate had risen to 88.3 percent in 2018, a jump of nearly 8 percentage points from 2017. It was the largest increase among Hillsborough’s 27 high schools, as the district pointed out in a news release on Dec. 21.

But the school had another distinction: Even as its graduation rate soared, its passing rate for ninth- and 10-grade students taking the state’s English language arts test — a key requirement for graduation — continued to hover around 30 percent. Last year, the gap between that passing rate and the graduation rate was the highest in the district.

Anderson worked for the district for more than a decade. He coached football and taught history at Brandon. He received a letter of reprimand in 2015 because of a personal relationship with a former student who had graduated and passed her 18th birthday, records show. The district’s professional standards office, while finding no basis for legal action, told Anderson it "perceived your flawed decision making as inappropriate and unprofessional.”

He joined the staff at Spoto three years later.

Because Spoto is an Achievement School, teachers are expected to give students uniform tests known as “common assessments” throughout each semester to make sure they are prepared for district exams in December and, ultimately, state exams in the spring.

Cherie Miller, a resource teacher, and the social studies department chair, Ross Webster, noticed Anderson’s U.S. History students scored much higher on the December exams than they had on the previous tests. They shared the numbers with supervisors at district headquarters.

The common assessment scores in Anderson’s classes previously had been the lowest in the school, with fewer than half of his students passing. Yet on the semester exam, they had a passing rate of 59.7 percent.

His students were out-scoring their peers at all but three of the district’s high schools. And they were 7 points higher than Miller’s students, even though she had been assigned to help Anderson improve his teaching.

Students began to talk, and four agreed to submit written statements.

Two wrote that Anderson gave out two or three answers during the exam because he had not covered the material. The other two described posters on the wall in plain view, containing test answers. And although one wrote that Anderson collected phones before the exam, that student said Anderson did not appear to make any effort to make sure the kids did not have a second phone, or a smart watch.

Testing supervisors interviewed Anderson on March 12 and found him “very candid,” according to their report. He said that throughout his teaching career he had left posters up for regular tests, taking them down only for state exams. He said this year’s exam was new and he had not been able to cover all the material.

“He was adamant that he did not think the semester exam was as ‘big a deal’ as the state tests that are given,'” the report said. Repeating that he always used posters, he said that “he really didn’t understand why that would be inappropriate on test day.” Nor, he added, did he do any of this for monetary gain.

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After his resignation, messages of support appeared on social media from students who said he had been set up. They posted videos of Anderson rapping in class, a practice he used in his teaching.

“I miss and love you guys too,” he told them in a message that was posted on an Instagram page called “bringandoback.” He urged them to study for the state end-of-course exam, and “stay focused on the goal. I’ll be good.”

The Tampa Bay Times was unable to reach Anderson and Perez for comment.

It has been a difficult year all around for Spoto, which has some of the lowest results in a survey teachers completed around the time Perez stepped down. Between 75 and 95 percent gave negative answers to questions about student behavior. Fewer than 17 percent agreed that “there is an atmosphere of trust and mutual respect” in the school.

As the district investigates his predecessor, Haggins is working to improve that atmosphere, said Alege, the deputy director who supervises Spoto. The new principal has been meeting with teachers individually and looking for ways to balance the school’s discipline problems with the need to make sure all students get the instruction they need, he said.

“Jaz’s goal is to listen,” Alege said. “And they have been receiving him very well.”

As for the students, he said, Haggins “is setting a tone for the school’s students. He wants them to know that they can have a good time. But when they misbehave, it will be addressed.”

Contact Marlene Sokol at msokol@tampabay.com. Follow @Marlenesokol.