They inspired her and pushed her when she felt like giving up. And when Salma Hussain delivered the valedictory speech at English High School in 2010, she singled out eight teachers who helped her rise to the top just four years after arriving in Boston from Bangladesh, speaking no English.

“My teachers were my second parents. They were the ones who always helped me, no matter what I needed,” Hussain said. “Ms. Pred-Sosa, Ms. Drew, Mr. McShane, Ms. Silas, Mr. Hogu, Ms. Rodriguez, Ms. Follenweider, Mr. Beyer. I will never forget what you did for me.”

Just two years later, seven of the eight teachers Hussain praised are gone, most of them casualties of a radical transformation under a little-tested, 30-something headmaster recruited by Boston school Superintendent Carol R. Johnson to turn around one of the most troubled high schools in the state.

An extraordinary three-quarters of English High’s teachers and administrators have quit or been let go during the past three years, school records show, as headmaster Sito Narcisse pushed through one controversial initiative after another — from school uniforms to single-sex classrooms to eliminating the grade “D,” forcing students to earn a “C” or fail. Teachers who did not go along with Narcisse’s approach were “not the right fit,” in his words, and he sent 38 of them packing, while dozens of others retired or resigned.

Now, Narcisse himself is leaving for a new job amid questions about the wisdom of letting someone so inexperienced carry out drastic changes. Standardized test scores rose slightly under Narcisse, but so did the dropout rate, the course failure rate, and the absentee rate — while the experience level and morale of his teachers plummeted.