Too many educators would have us believe poor children can't learn. Or can't learn well. Or can't learn except at a great price. But across the nation dozens of principals of low-income schools are proving that poverty is no excuse for failure. Take P.S. 161 in Brooklyn. Nearly 100 percent of the children come from low-income families, yet this year's sixth grade class had the second highest reading scores in all of New York state. "It's a lot of garbage that poor kids can't succeed," says Principal Irwin Kurtz, who came to the school 13 years ago when students were testing in the bottom 25 percent among schools in Brooklyn's District 17. Today they score in the 71st percentile in reading and the 78th percentile in math. Equally dramatic success stories can be found in Chicago, Houston, Detroit and other cities.

I recently interviewed more than 100 principals of high-performing, high-poverty schools like P.S. 161, looking to identify those practices that make a school a center of academic excellence. I wanted to find schools where at least 75 percent of the students come from low-income families but score in the top third on national exams. Typically, schools with this many low-income students score in the bottom third.

The children in the high-achieving schools I found come from typical inner-city neighborhoods. They are predominantly African-American or Hispanic. Many of them even live near failing public schools that draw from the same local population. So what explains their success?

My visits to these schools uncovered seven common traits:

Principals must be free. Effective principals decide how to spend their money, whom to hire and what to teach. They are either given their freedom or take it for themselves. Principals whose schools develop a reputation for academic achievement are usually left alone. But to get there, great principals are often mavericks who buck the system or low-fliers who get the job done quietly.

Principals use measurable goals to foster achievement. High expectations are one thing - a relentless pursuit of excellence is another. High-performing schools focus on tangible goals. Whether it's calculus by 12th grade, a fluently bilingual school, literacy at the earliest age, or all students working above grade level, great schools set specific benchmarks the whole school must reach.

Master teachers bring out the best in a faculty. Improving the quality of instruction is the only way to improve overall student achivement, and teacher quality - not seniority - is the key. Effective principals scour the country for the best teachers and design their curriculum around the unique strengths and expertise of their staff. Good principals turn their schools into schools for teachers.

(Parenthetically, I might add here that I am not sure that a school's curriculum should be designed "around the unique strengths and expertise of their staff." I think the school's curriculum should be objectively chosen for its merit. Well educated teachers should then be chosen who will creatively - using their unique strengths and experitise - teach the content of the curriculum.)

Rigorous and regular testing improves student performance. Testing is the diagnostic tool that best enforces a school's goals. Regular tests at all levels and in all areas ensure that the prescribed curriculum is being communicated in every classroom. Mock tests are usually administered three or four times a year to prepare for national exams.

Achievement is the key to discipline. A "command-and-control" approach to discipline is limited to the number of security guards you can hire. When self-discipline and order come from within, every person is part of the solution. Schools must teach by example that self-control, self-reliance and self-esteem - all anchored in achievement - are the means to success. Success, in turn, inspires confidence, order and discipline in students.

Principals work with parents to make the home a center of learning. A lack of parental involvement is often the first excuse for poor performance. Effective principals overcome this by extending the mission of the school into the home. They establish contracts with parents to support their child's efforts to learn.

Effort creates ability. Good principals demand that their students work hard. Long days, extended years, after school programs, weekend programs and summer school are all features of ourstanding schools. Effective principals eliminate social promotion. Students must fulfill specific course requirements to advance.

Outstanding principals know that all children can excel academically regardless of race, income level or family background. Studying their success should be the highest priority of educators in a country where more than half of all low-income fourth graders cannot even read. Nothing I've described is beyond the reach of any school in America. But if we are to see more such schools, we need to stop making excuses for failure.