IN American public education, it has been said, geography is destiny. Students in middle-class or affluent neighborhoods receive a quality education. But students in poorer surroundings, especially in the inner cities, receive a correspondingly impoverished education.The education gap is attributable to a number of factors, but the most obvious is the disparity in funds that flow to schools from local property taxes. Although the funding divide is not a new issue, the gulf in per-pupil spending between America's richest and poorest school districts is widening. In many states, schools in property-rich districts spend more than twice as much per pupil as schools in poor districts, even though property owners in the poor districts often are taxed at a higher rate. One result has been a flurry of lawsuits challenging states' school-finance systems as unfair. Challenges are pending in 22 states; the issue has been adjudicated in nearly 20 other states since the '70s. Because the Supreme Court declared in 1973 that unequal funding of public schools doesn't violate the US Constitution, subsequent challenges have been mounted under state constitutions. They are based either on "equal protection" clauses in state charters or on provisions requiring states to establish school systems characterized by such words as "thorough" or "suitable." Constitutional assaults on states' methods of funding public schools have met with mixed results. In 10 states courts have ruled that school-finance systems are unconstitutional, but challenges have failed in 12 other states. Happily, the tide seems to be with those demanding that state governments more equitably distribute education dollars among school districts. Since 1989 the highest courts in Kentucky, Montana, New Jersey, and Texas have ruled that the school-finance systems in those states were unc onstitutional, while courts ruled the other way only in Oregon and Wisconsin. Defenders of traditional school-finance systems, based heavily on local property taxes, note the long American tradition of local control of schools, whereby the "consumers parents - can directly influence the quality of the "product." To the extent that redistribution of resources to achieve equity in education comes into conflict with achieving excellence, they say, a "nation at risk" has to favor excellence. And they point to studies purporting to prove that levels of spending in schools have little e ffect on achievement as measured by test scores. However, these contentions do not rebut the manifest need for greater fairness in the funding of America's public schools. Even with some redistribution of property-tax revenues and greater influx of state tax dollars, parents and local educators can maintain a great degree of local control of schools. Nor are equity and excellence mutually exclusive: Sacrifices can be made by the wealthiest school districts without impairing core quality. And the nation will remain "at risk" and competitively disadvanta ged if students in poor districts continue to fall further and further behind. As for the argument that in education "input" bears little correlation to "output," the claim - a favorite of some conservatives - is too narrow. SAT and other standardized-test scores aren't the only measurements of the quality of a child's schooling. Money spent by schools for computers, language labs, music and art courses, sports, counseling, and other specialized offerings may not raise test scores, but can make a vast difference in a child's education and life. Of course, it's one thing for state courts to mandate changes in school finance, and quite another for legislatures to devise fair and effective new methods. Remedies are both politically and fiscally hard, especially when states already face heavy new demands in areas like health care and corrections. We recognize the problems. And we know that money alone will not solve the problems of the nation's worse schools. Yet it is unacceptable that many children in America are receiving sadly underfunded educations, simply because of their street address.