“My name is Lady Bird.”

“Is that your given name?” the teacher asks.

“Yes, it was given by myself to myself.”

Right away, we know we’re going to spend the next hour and a half with a free-spirited teen who attends an all girls’ Catholic school, where free spirits like Lady Bird have for centuries been kept locked inside uniforms of gray skirts and navy blazers until they either fly away and shake up the world or simply succumb, get married and send their children to the same school.

Let me say right away that everyone and everything in “Lady Bird,” written and directed by actor Greta Gerwig, is simply great, not just good — especially Saoirse Ronan in the title role — but great, as if they were born to play these roles. Even the drug store clerk, the extras walking the streets and halls, everybody.

The script, billed as semi-autobiographical, is perfect. The lighting, editing, make-up, the Catholic girls’ school uniforms, which if you ever dated such a creature, will send a chill up your spine.

Lady Bird lives in Sacramento,California, probably in 2002, and even now it’s the dullest city in the state.

Lady’s hair looks as if she cut it in anger and then dyed it a shade of neon red. Lady tells everyone she lives on the “wrong side of the tracks,” but that doesn’t mean what it used to mean. A railroad line slashed right through downtown Beverly Hills for years. Lady Bird’s house is clean and neat, the lawn well mowed, but when a wealthy friend visits, she comments, “You live here?”

Daddy (Tracy Letts in yet again another beautifully written part) suffers from middle age, clinical depression and has been out of work for a year.

To make herself feel better, Lady has begun abandoning her best friend, an overweight frump (Beanie Feldstein), and gone to hang with the cool and hip crowd in her all girls’ Catholic school, hoping whatever it is they have is catching.

Her mother, Marion (Broadway legend Laurie Metcalf, a born scene-snatcher), is an overworked night nurse in a psychiatric hospital and has her own uniform, a slate blue nurse’s pantsuit she seems to have been born in. She is, of course, from a generation that took it all on the chin and wears the bruise like a medal. Marion spends her days dealing with it all — the hospital, her husband, her rebellious Lady Bird — and each line around her mouth shows it.

Marion has been holding family and dad together for so long she’s lost track of all the numbers on life’s calendar. One day looks like another. Yes, you already recognize her, and when you look closely over the next very short hour and a half, you’ll come away wet-eyed and heart-scarred by how familiar she is. You know a Marion. You yourself may be a Marion.

Despite her daily efforts, and probably because of them, the mother-daughter bond between them is fraying at the edge. It’s safe to say that every mother and daughter in every audience will see themselves in Lady and Marion. That’s what makes a movie great.

Both are strong-willed and raging against the weight of the new economy that doesn’t give a damn.

As I have said, I always found Greta Gerwig out of place in all of her roles. Now I know why. Greta is an artistic “trans,” someone who has long been an auteur trapped in an actor’s body.

But now she’s out and making critics’ and audiences’ hearts flutter. “Lady Bird” has gotten a 100 percent rating in Rotten Tomatoes. I often disagree with that rating, but this time I think they’re on to something.

Of course, this is her story. Nobody but you can get your story right, and her next may fall, but while skeptics are waiting for her to fall, she’s soaring. Come see her Lady Bird once, and you’ll come back again, then rent it and buy it. A perfect little movie, how wonderful is that?

J.P. Devine of Waterville is a former stage and screen actor.