CAMBRIDGE, Mass. - This city has joined a small but growing movement to use income, not race, as a primary factor in assigning students to schools.

… Noah's assignment to Fletcher-Maynard was primarily driven by his family's income, but it also helped the district meet another goal for the school: greater racial balance. Noah is white. Fletcher-Maynard's 264 students are predominantly black or Hispanic.

… Proponents of economic integration say there is ample evidence that all children learn better at schools where middle-class students are in the majority.

"While there are a handful of exceptions, in general high-poverty schools don't work," said Richard D. Kahlenberg, an educational researcher at the Century Foundation who is a leading advocate for economic integration as the way to raise achievement among poor children.

… But critics say that the way to help low-income students make educational gains has to be more effective teaching - not moving children around. "There's something wrong with the assumption that if you've got too many low-income kids in a classroom, you can't teach them," said Abigail Thernstrom, a senior fellow at the Manhattan Institute who has extensively researched race and education. "My response to that is: No excuses. Start to educate the kids."

Dr. Thernstrom and others also say that economic integration has no relevance for large, predominantly poor urban school districts like Detroit, Chicago, Los Angeles and Washington. "What are you going to do - helicopter the kids in?" Dr. Thernstrom said. Supporters of economic integration counter that children in poor urban areas should have the opportunity to cross district lines and attend middle-class schools.

Just as racial integration of schools was resisted by many whites, middle- and upper-income families may object to economic integration. Moreover, some civil rights advocates say that economic integration does not go far enough in achieving racial integration.