Waiting for “Superman” –– a documentary about failing government schools — was directed by Davis Guggenheim, who also produced An Inconvenient Truth (promoting Al Gore’s “global warming” scare). “Superman” has won lots of awards and Jonathan Alter, a man of the left, was a featured commentator. Yet the film, which adds to the general discomfort of teachers unions, has also won approval from conservatives.

It’s a measure of how far government schools have sunk in the public esteem that liberals have become alarmed enough to make a documentary that the American Federation of Teachers dislikes. Problems caused by teachers unions have been overlooked for years, and a film highlighting them is praiseworthy. Yet I also felt there was some confusion about the project. Let me try to say why.

“Superman” follows the fortunes of five families mostly from poor backgrounds, but with mothers (grandmothers?) hoping to rescue offspring from bad schools. And they have found the solution: Charter schools. But they are oversubscribed. One child is among 792 applicants for 40 slots in the Harlem Success Academy. So the cameras take us to public lotteries, where mothers and their offspring are anxious spectators. A child just might but probably won’t be admitted to the charter school of his choice.

“The political message is unambiguous,” Robert Weissberg wrote for the American Thinker. “Why permit only a few lucky kids to escape horrific schools? Every American kid deserves better, so abolish barrier-like lotteries and make good schools universal.”

An emeritus professor of political science at the University of Illinois at Urbana-Champaign, Weissberg recently wrote a politically incorrect book, Bad Students, Not Bad Schools (Transaction Publishers). His “guess” is that charters “are largely a silver-bullet hope among today’s public school stragglers”; in other words, a hope that probably won’t fulfill its promise.

Nonetheless, the movie reposes great faith in charter schools. It’s hard to generalize about them, because they are “chartered” by the separate states, with diverse regulations. They are taxpayer supported, but many of the usual union and school-district regulations are in abeyance. So they are freer. Some are also supported by mega-philanthropists such as Bill Gates and the Walton (Walmart) family.

About 5,000 charter schools exist today, disproportionately attended by black and Hispanic students. A Stanford University study showed that about 20 percent of charter schools do better than regular public schools, but about 35 percent do worse. “Quibbles about the uncertain value of charter schools aside,” Weissberg writes, “charters here [in ‘Superman’] are clearly the heroes, and public schools the villains.”

I visited a charter school in New Orleans in 2007. Most of the public schools, already dysfunctional, had been wiped out by Hurricane Katrina. So charters were given unusual latitude. To judge by the school I saw, well located in the French Quarter, a great deal of idealism had been unleashed. Teachers arrived early and stayed late, gave out cell phone numbers to students and answered homework queries at all hours. There was attention to neatness and order; classes even met every other Saturday. As to how things would work out, it was still early days.

The eager principal who showed me around had actually gone into the nearby (dangerous) Iberville housing project to recruit students. He is no longer at the school. My guess is that in the long run enthusiasm, even when effective at first, won’t be enough to overcome a fundamental defect.

Over the years we hear of “superman” principals who come to bad schools and rejuvenate them by personal example, inspiration, and discipline. But idealism fades and energies dissipate. A properly functioning system — as the U.S public school system was for many decades — must work with ordinary people and everyday incentives, not with extraordinary people who are somehow inspired. After a few years they can burn out like a spent rocket.

In Bad Students, Not Bad Schools, Weissberg says that some of the “kids” presently occupying classrooms, “disdaining academic achievement” and often disrupting proceedings, should be “shown the door.” But in a society where diplomas-for-all is a priority, that is unthinkable. It is not poets but taboos that are the unacknowledged legislators of our day. And thinking that whole classrooms of “kids” are just not going to make it is forbidden.

Schools have become “the refashioned Great Society,” says Weissberg. He means that rewarding idleness in the name of abolishing poverty is now unpopular but has been replaced by a new ideal that currently prevails: “no child left behind.” It also “puts bread on millions of tables” — full employment for the education industry — so “slackers must be retained regardless of educational value.”

Worse, retention is embraced even if this impedes learning among their classmates. To be grossly politically incorrect, most of America’s educational woes would vanish if these indifferent, troublesome students left…

But that is unthinkable, “so we lurch from one guaranteed failed reform to the next, squandering hundreds of billions of dollars.” Progress, pols assure us, is just over the horizon; meanwhile failure attracts more funding. Weissberg blames “slothful, sometimes disruptive students,” and recommends throwing out “the bottom quarter of those past 8th grade.”

I DON’T GO all the way with Weissberg because he brings up another taboo, IQ. But many black children suffer from a disadvantage so acute that intelligence isn’t needed to explain anything. At lower income levels, black family life has been all but destroyed, often leaving neither parent in sight and grandma holding the baby. Only 17 percent of black children grow up to be teenagers with both parents still in the home. So the great hazard for charters, as I see it, is that as long as their students come from broken homes, especially those lacking fathers, they are likely to provide little more than an uptick in academic results, and perhaps a brief one.

The problem with incipient gang members sitting in classrooms, and planning to outwit rival gangs, not to mention the police, is not that they are unintelligent but that they plan to join the lawless world they grew up in. They are not interested in Henry VIII or quadratic equations.

Private schools can kick out disruptive or failing students. Government-funded schools essentially cannot. As long as our regnant ideology of equality prevails, government schools will be nearly unreformable. Weissberg makes the comparison with public housing. If bad students cannot be removed, ghetto schools will resemble public housing projects.

Urging that adults must get married before having children is an ideal that is now too remote for mere lawmakers to address, let alone restore. Only a recovered religious faith will be able to do that. Book learning won’t be attainable in government-funded ghetto schools, no matter how powerless the teacher unions become.

I spoke to an old friend, Bernard Ruffin, who taught at a Fairfax County (Virginia) public school. He recently retired with a pension and a sigh of relief. A man of intellectual accomplishments, he has degrees from Bowdoin and Yale and has published eight books. His mother was an administrator at Howard and two aunts taught at Dunbar High School, the elite black high school in D.C., since destroyed by egalitarian madness. Yet Ruffin was relegated to the “ghetto” section of his school. Administrators want to reward their (younger, more pliant) favored teachers by assigning them to the best students.

Ruffin found it impossible to teach his pupils for the few hours a week he saw them. Often at school “for social reasons,” they took the attitude: “I defy you to teach me anything.” Faced with faculty complaints, administrators sided with students (to minimize political repercussions). Ruffin knew that when pupils came from broken, fatherless homes, “the teachers were blamed for the faults of the parents.”

Let me repeat the words of Washington Post columnist and Dunbar alumnus Colby King: “We have to fix the family. There’s no getting around it. The school system can’t solve it. The police department can’t solve it, the social service agencies can’t solve it.”