The black-and-white subway ads for the NYC Teaching Fellows program were, if you recall, heavy-handed, even a little bit cruel. Also, frankly, not as well punctuated as they might have been. “You remember your first grade teacher’s name. Who will remember yours?” they asked, taunting vulnerable commuters with the anonymous worthlessness of their pursuits.

Even so, there was a kind of genius to them, because don’t most of us remember our earliest teachers? Not just first grade, but all the way up to the threshold of high school, when things got unavoidably diffuse. These people fed our young brains and shaped our characters, for good or for ill.

It’s that kind of ineradicability that’s at the ebullient, comic heart of Sarah Shun-Lien Bynum’s utterly winning “Ms. Hempel Chronicles” (Harcourt, 193 pages, $23), a wistful story cycle of a novel that’s part paean to learning and the power of language, part meditation on the many selves it’s possible to be in a lifetime, part ode to the sacred, fragile beauty of memory.

For Ms. Hempel (first name Beatrice), a tender, intrepid, sometimes dangerously misguided young middle-school teacher in New York, the ineradicability goes both ways. Just as she’s become a part of her students, they’ve become a part of her: “She would never forget their names, even years and years later; they were carved roughly and indelibly somewhere.” Also, she loves them — loves them so well as they are that she greedily resists the notion of their growing up even as she plants in them words (amnesiac, benevolent, depraved) that she means to live in their vocabularies for the rest of their lives.

Here she is on a field trip to the beach with her students: “Ms. Hempel held their towels in her outstretched arms and rubbed their backs when they scrambled, dripping, up from the water.” And later that day, standing at a distance as a clump of boys, defiantly naughty, builds a penis out of sand: “They glanced over, again, in Ms. Hempel’s direction. They even cleared a little space for her so she could stump over to the penis and object. But didn’t they know? She was the young teacher. It was her job to indulge them, to be impervious to shock, to watch all the same television shows that they did.”

Yet this prim punk rocker manqué, this grown-up who isn’t quite finished growing up, is not all that dedicated to being a teacher. And so she looks wildly for an unimpeachably honorable out, even a temporary one. Her drab little fiancé, Amit — who is, we suspect, not truly good enough for her — urges her to call in sick with a cold when she’s dreading going to school, but Ms. Hempel trains her fantasies on more dramatic, bigger-ticket excuses: an accident that puts her in a body cast, maybe.

These conflicted feelings would come as a dismaying shock to the seventh- and eighth-graders she introduces to the joys of literature (Tobias Wolff’s “This Boy’s Life,” salty language and all) and critical thinking (a mock trial involving anthrax and national security, back when that combination was mostly a hypothetical). Old enough to feel invulnerable, they are still too young to have erected defenses that would keep their teacher from lodging in their affections, and far too young to imagine that teaching them might not be enough to sustain her. But as Ms. Hempel and Ms. Bynum know equally well, both life and good writing are necessarily complicated, filled with contradictions and emotional ambiguities.

Ms. Bynum’s novel is filled, too, with exquisitely vivid portraits in miniature: swift brushstrokes that become Harriet Reznik, seventh-grade magician; Mr. Meacham, fellow teacher and relic of a more elegant age; Melanie Bean, betrayed and disappointed mother of middle schooler Will. They are no more than glimpses, really, but they have depth and dimension; these minor characters pulse with the life we’re sure they lead somewhere in the background.

Others get more stage time: Ms. Hempel’s father, now dead, who was her childhood co-conspirator and the source of her overexuberance; her charmingly peculiar little brother, Calvin, given to playing cat burglar in the black of night when they were growing up; sweet, troubled Jonathan Hamish, a student as attached to Ms. Hempel as she is to him, a bad boy who doesn’t want to be one. “What set him apart was his shame; he took no pleasure in his bad behavior. When his classmates gleefully recounted his misdeeds — Jonathan chucked a blueberry bagel at Mr. Kenney’s head! Jonathan got sent out of theater class for the sixteenth week in a row! — he would retract into himself, refusing to look at Ms. Hempel, his face darkening. He never felt the triumph that the other kids believed was his due.”

Ms. Bynum, whose unconventionally structured first novel, “Madeleine Is Sleeping,” was a National Book Award finalist, here creates a seamless, intuitive novel of short stories, several of which have been published elsewhere individually. Each is a small, gorgeous thing on its own, but the wise and whimsical “Ms. Hempel Chronicles” gives them their collective due, deploying them on a broader canvas, their colors more layered, their impact more powerful. Stepping back from it, we see something we couldn’t have detected before: Ms. Hempel’s students feed her young brain; they shape her character, too.