Nothing is more gratifying for a teacher than to have a former student look back on formative times and think, “I’d really be a different person right now, were it not for Mr. So and So.” But the idea that that teacher could be Tony Danza, of “Taxi” and “Who’s the Boss?” fame, is a bit tricky. We tend to typecast teachers, associating them with tweeds or dusty lab coats and hands perpetually coated in chalk dust, so a memoir about the teaching life — and grind — from a Hollywood sitcom star takes some getting used to.

In theory. Because, in reality, about four pages into what’s tantamount to a prose-based documentary — “I’d Like to Apologize to Every Teacher I Ever had” — you’re sure to feel as if you’ve squeezed your adult self into one of those weirdly shaped student desks, hoping today is not the day Mr. D drops that pop quiz on you.

There’s a streamlined premise here: Danza loses a TV gig, wonders what to do with himself, contemplates a difficult family situation — he’s separated, with two kids — and decides to make up for past transgressions against his former teachers and, touchingly, his earlier, more reckless self. And so it’s off to teach 10th-grade English in Philly’s hardscrabble Northeast High, a school that has its students pass through a metal detector each morning. Honorable intentions quickly give way to chaos, and no shortage of tears from the students and Danza himself. Despite his affability, he ends up going through a crisis of the soul, against a backdrop of brawling girls, break-dancing students and a would-be Lothario who can’t keep his hands to himself on the field trip bus. And, oh yeah, there’s a TV crew shooting the proceedings for an A&E series, but they bail half-way through the school year, complaining that there’s not enough drama.

But that’s a reality-TV conceit, the need for easy story lines, whereas there’s nothing easy about teaching at Northeast High or being a student there. Anyone expecting Danza to mug his way through the year is bound to come away shaken by the man’s sincerity. And he has a knack for turning a phrase. When Danza visits a bright, wayward kid held in the school jail (seriously), there’s a Dantean vibe of wandering around the Inferno fitted out with No. 2 pencils and overhead projectors.

Overwhelmed, Danza solicits all the input he can get from his fellow teachers, and we start to see how close a teacher is to being a student and vice versa. “They offer advice and tell me what they believe it takes to be a good teacher. ‘You have to be prepared to play many roles,’ says an older woman who’s been teaching for decades. ‘You have to be a mother, father, sister, brother, social worker, counselor, friend and anything else they need.’ ”

‘I'd Like to Apologize to Every Teacher I Ever Had: My Year as a Rookie Teacher at Northeast High’ by Tony Danza (Crown)

That includes policeman, as when a student tries to goad Danza into a fight. You think, Oh no, one of the cabbies from “Taxi” is going to pop a high school kid in the mouth. But self-discipline prevails, and we see a special, pedagogical kind of will on every page: the will to face a student’s horrifying, out-of-school problems, or the will to devote hour upon unofficial hour to help a kid learn to read and, just as important, to feel good about herself. As they all do when they manage to memorize a poem. One girl is so overcome with emotion that she needs a couple of breaks out in the hall to get through her recitation. Meanwhile, Danza makes a compelling argument for the exercise: “It’s the difference between a pianist playing while reading the sheet music and a pianist playing a piece he has memorized. If you know it, you feel it in your body as if it’s a part of you.” One might add that there is something poetic about being a teacher, especially one who becomes a part of who we are.

Fleming writes for the Atlantic, Rolling Stone, ESPN The Magazine and other publications.