School children used to be the ones who gave lame excuses for not doing their work. Now it's their principals and teachers. Ask these "professional educators" why so many children from low-income African-American and Hispanic families fail academically, and the excuses begin: Too many kids. Not enough money. No parental involvement.

Fortunately, some educators haven't given up. They accept "no excuses" for failure.

The Heritage Foundation recently profiled seven of these principals. Their schools all show that educators who expect - in fact, demand - excellence from their students usually get it.

How well do these students perform? Nationwide, public schools with low-income student populations score, on average, below the 35th percentile on national exams. We found low-income schools where they score in the 65th percentile or higher. At three of the schools, the number of low-income students is close to 100 percent.

Some educators may want to dismiss these students as statistical anomalies - exceptions to the widespread assumption that only "rich kids" can succeed in school. But good schools don't become outposts of academic excellence by accident. The principals who run them simply refuse to tolerate failure. And they don't consider themselves magicians; other low-income schools can duplicate their success, they believe.

So how do these principals do it? Here are a few of their secrets:

They reject the idea that low-income students can't succeed. "Economic status has nothing to do with intellectual ability," says Hellen DeBerry, former principal of Earhart Elementary in Chicago. From crowded classrooms to shoestring budgets, nothing stands in the way of producing students who excel.

They create an "atmosphere of learning." Their schools are neat and orderly, and uniforms are often the rule. At the Crown School (P.S. 161) in Brooklyn - which has "an aura of gravity," according to The New York Times - student awards and presentations fill every hallway. Gregory Hodge of the Frederick Douglass Academy in New York City enforces "12 non-negotiables," including an exhortation to "learn to disagree without being disagreeable."

They hire the best teachers available - then allow them to teach as they see fit. For these principals, teacher quality supercedes seniority. Because they're interested in results, they refuse to dictate a particular style or method of teaching. In return, teachers are obligated to make children learn. "They know they have to teach until kids get it," says Michael Feinberg of the KIPP Academy in Houston.

They use rigorous and regular testing to ensure student achievement. Mock tests are administered several times a year to help prepare for national exams. "You have to set clear and measurable goals for everyone," says Crown School Principal Irwin Kurz. "I don't know what other people use. We use tests."

They make sure the home is a "center of learning." Every effort is made to involve parents, from checking homework to reading to their children. Feinberg has students, parents and teachers sign a pledge to "do whatever it takes to learn." At Cornerstone Schools Association in Detroit, parents sign a "covenant" committing them to help their chidren pursue academic excellence.

"It's a lot of garbage that poor children can't succeed," says Kurz. In the end, that may be the most valuable lesson of all.