A neuroscientist tells the story, captured on film, of interacting with a 42 MINUTE old baby, sticking his tongue out and the infant, eyes barely adjusting to the big wide world, mimics him.

Academics, doctors and teachers talk about how such early “learning” begins with babies, how intense it is in those first days, weeks and years.

“Executive Function” in learning is explained, the socializing and problem-solving that children need to master (“Self Control,” “Working Memory” for instructions, being able to retain and follow them, and “Mental Flexibility,” mastering the ability to shift focus, adapt to a new situation).

Teachers and parents marvel at how much more prepared for life children are who have heard millions, rather than hundreds of thousands, of words before they ever reach the school system.

Retired military officers, members of a lobbying organization called “Mission: Readiness,” talk about an American generation unprepared and unqualified to serve, much less grab great jobs that help make the country competitive. The problem, as they see it — echoing EVERYbody who has appeared on camera before them — is a nation that neglects early childhood education.

And then we meet the energetic young people, teachers at the bottom of the educational ladder — by reputation, clout and pay grade — fighting the fight to rectify this social failing in a career that to them is a calling, but a calling that requires them to live with their parents or take second jobs.

“No Small Matter” is a brisk, smart and entertaining documentary about the importance of early childhood education, the ways investing in it pays dividends in social, economic and civic terms and the costs that failing to take it seriously are imposing on us.

This film was finished long before the phrase “defund the police” hit our political discourse, but this is what a deeper discussion of the divisively-labeled idea is about. Spend on childcare, improve it and make it available to every parent in America, and you won’t need legions of police, tactical gear and tanks to keep order in our cities.

The evidence is there and it’s overwhelming. “No Small Matter” doesn’t need to go abroad and show us other countries that are taking this more seriously and the (good) consequences of such policies. We meet an alumnus of The University of North Carolina’s “The Abecedarian Project,” a nearly half-century-long (and counting) study of children who participated in stimulating, nurturing pre-school care, and those who didn’t.

Race and social class become less important in determining a child’s future when they’re in great day care before kindergarten. They grow up to be better educated, higher earners, less likely to have had any problems with the law.

Filmmakers Jon Siskel, Greg Jacobs and Danny Alpert take us into classrooms and homes and brain research labs and cram a lot of breezily-presented facts, figures and arguments in “No Small Matter’s” brief 72 or so minutes.

Teachers play-act childish arguments and start that “Executive Function” problem-solving ball rolling with their students. Cookie Monster shows up to interrupt over interview and demonstrate impulse control. Advocates earnestly advocate.

The profession of early childhood educators is redefined, once and for all.

“They’re not baby-sitters. They’re brain-builders.”

If everybody were to see this one teacher at her second job, bar-tending, maybe we’d get it. If we all could hear tearful tales of how no one can build a career doing this vitally important work, forced to live with your parents in order to survive on $30,000 a year, after ALL the arguments showing us how vital and very important this, maybe we’d see the need to change our priorities, where we’re spending our tax dollars.

Because if there’s one fact everyone should absorb from this sometimes-cutesy documentary, it’s that this big hope for a better, smarter, fairer and healthier America is “No Small Matter.

MPAA Rating: unrated

Cast: Narrated by Alfre Woodard.

Credits: Directed by Danny Alpert, Greg Jacobs and Jon Siskel. An Abramorama release.

Running time: 1:11