The top-grossing movie over the Martin Luther King holiday weekend was “Coach Carter,” the inspirational film based on the real-life experiences of a Richmond, Calif., businessman and part-time basketball coach who uses his power over impoverished inner-city athletes to insist that academics come first. Real men, he insists, do the hard work of investing in their brains, not just their muscles.

But perhaps the more meaningful message these days is being delivered by actor Bill Cosby – the Chet Kincaid of the wildly successful 1969-1971 sitcom “The Bill Cosby Show” – who is crisscrossing the country demanding that poor inner-city parents take responsibility for making sure their children arrive at school ready to learn.

Most recently Mr. Cosby was in Detroit, where a capacity crowd of 1,800 cheered his admonition to “stop the foolishness” and quit blaming others for the educational deficit suffered by many minorities. “It’s not what they’re doing to us. It’s what we’re not doing. …If your child is walking around in thousands of dollars worth of clothes and doesn’t have a dime’s worth of sense, he’s talking to you.”

It’s a message totally in line with the middle-class values expressed by Coach Kincaid, the fictional gym teacher of 35 years ago. But the fact that the clearly frustrated Cosby is saying such things out loud – and so bluntly – rankles severely in certain quarters. When Mr. Cosby launched his crusade last May at Constitution Hall in Washington on the 50th anniversary of Brown v. Board of Education, Naacp officials on the dais reportedly sat “stone-faced” as he ranted: “The lower economic people are not holding up their end of the deal. These people are not parenting. They are buying things for kids – $500 sneakers, for what? And won’t spend $200 for ‘Hooked on Phonics.’ “

There was similar reaction when Mr. Cosby brought his road show to Detroit last week. Even before Mr. Cosby had appeared, a Michigan State professor of urban affairs objected that Mr. Cosby’s “sweeping generalizations … may be providing ammunition to mean-spirited policy-makers wishing to justify withdrawing any remaining assistance to a group they have always considered undeserving.”

In fact, however, support for public schools has been marching forward far faster than the rate of inflation for decades. And while Mr. Cosby, who grew up poor in Philadelphia, knows full well that there are racists out there ready and willing to exploit his message, he rightly asserts that’s irrelevant. “I tell you,” he pointed out to Detroiters, “now 87% of the city is black. We are not a minority.” In other words, the time for excuses is over.

That doesn’t answer the important question of what, exactly, is to be done? Here, both Mr. Cosby and Hollywood come up a bit short.

As I watched “Coach Carter,” my mind reeled back to a very similar film, “Stand and Deliver,” the 1988 classic about another inspirational school leader, Jaime Escalante, at Garfield High School in East Los Angeles. The movie showed Mr. Escalante successfully challenging a class of underprivileged, undereducated, and mostly Latino students to work hard enough to pass the Advanced Placement calculus exam, thus opening the way to college and opportunity.

But in a follow-up article in Reason magazine two years ago, writer Jerry Jesness pointed out that Mr. Escalante’s success was no overnight phenomenon. It had followed years of patient, difficult preparation. And when the teachers union and administrators blocked efforts to expand the program or compensate Mr. Escalante for his exceptional success, he left the school only a few years later.

To its credit, “Coach Carter” includes an unsparing indictment of a demoralized school bureaucracy that is content to pass students along rather than challenge them. And Mr. Cosby is right to challenge the values of parents who pay $500 for basketball shoes but not a cent for speaking the King’s English.

But clearly the problem is not just the parents (or, all too often, the parent), most of whom care deeply about their children even if they themselves don’t quite understand that an education begins at home. The problem is also an unresponsive, uncompetitive, uncaring public school system whose administrators and unions make it as difficult as possible for even concerned parents to get a decent education for their children.

But don’t stand on one foot waiting for Hollywood, or even the courageously outspoken Mr. Cosby, to take on such bastions of “progressivism” as the unions or the need to break up the public school monopoly.

Mr. Bray is a Detroit News columnist.