The thorny issue of school vouchers is back before the Supreme Court, and you know what that means: Every desperate argument against giving parents a choice over where they send their children to school is back before the public.

One of the most persistent is "skimming" -- the notion that school choice harms the children left behind because only the best, most motivated students transfer out. The New York Times' Richard Rothstein, for example, recently made a case for skimming in the article "The Other Side of Choice: After Top Students Leave."

But the "skimming" argument doesn't pass the test. Overwhelming research shows that school-choice programs serve the very students who need them most. The parents most likely to move their kids into higher-performing schools are the ones whose kids have struggled in their neighborhood schools. Those who excel tend to stay put.

"The students in the choice program were not the best, or even average students from the Milwaukee [public] system," says John Witte, an evaluator for Milwaukee's Parental Choice Program. "Rather than skimming off the best students, the program seems to provide an alternative education environment for students who are not doing particularly well in the public-school system."

A report by Wisconsin's Legislative Audit Bureau in 2000 found that Milwaukee's school-choice program serves a student population that is demographically identical to the city's public-school students. According to Kaleem Caire and Howard Fuller of the Black Alliance for Education Options, the program is used solely by children from low-income families, more than 80 percent of whom are racial and ethnic minorities.

But even if "skimming" was occurring, how would it represent an argument against school choice? If a boat is sinking and there aren't enough lifeboats to go around, should we let everyone drown? Rothstein and others seem to suggest that if school choice doesn't directly benefit every child, then no child should be allowed to benefit. This is preposterous. We can't, as the saying goes, let the perfect be the enemy of the good.

The goal of school choice is to help as many children as possible, either by providing them with the means to attend a quality school or by forcing their low-performing school to improve. And that's what school choice is doing. Just ask the parents of the 10,000 children in Milwaukee and 4,000 children in Cleveland who use vouchers to attend a school of choice. Ask President Bush, who has called for a $50 million school-choice demonstration project in this year's budget and a $2,500 tax deduction for families with children in failing schools.

A number of school-choice critics, including Rothstein, have conceded that competition spurs public schools to work harder to attract and retain students. A Manhattan Institute study of Florida's school-choice program found that the worst-performing public schools -- those where the jobs of teachers and administrators were on the line if their schools didn't improve -- saw test scores jump more than twice as much as other public schools in the same district.

And Carolyn Hoxby, the Harvard education economist who has studied Milwaukee's program, has concluded that competition from private schools and among public schools clearly boosts student achievement.

School choice has been particularly helpful to low-income and minority children, the students most likely to be trapped in failing schools. Harvard University's Paul Peterson studied privately funded voucher programs in New York City; Dayton, Ohio; and the District of Columbia, and found that minority children who used vouchers to attend private schools showed significant academic improvement.

New York City's Catholic schools "are more effective in severing the connection between race or income and academic performance [than public schools]," said Professor Joseph Viteritti, who led a New York University study that found Catholic school students -- regardless of income -- outscored public school students on the state's fourth and eighth grade standardized tests.

School choice is designed to rescue as many students as possible from drowning in failing schools by providing them the best education possible. Despite what Richard Rothstein and others may believe, school choice is not a zero-sum game -- everyone can win.

The answer is not to keep students who want a better education from going elsewhere. Competition shows great promise. It can help our students -- all of them -- get the world-class education they deserve. Why stand in the way of excellence? 

Jennifer Garrett, a domestic policy researcher at The Heritage Foundation (www.heritage.org), is the co-editor of "School Choice 2001: What's Happening in the States," a Heritage guidebook on school choice.