THE DEBATE over school choice—the hottest item on the American education-reform agenda—has unfortunately generated more heat than light.  Endorsed by presidents Reagan and Bush, by the nation’s governors, and by many business leaders, school choice is strongly resisted by the National Education Association, by many civil rights leaders, and by most public educators. Supporters and opponents alike spin abstract scenarios in which choice will either solve the ills of American education or send it into a rapid decline.  They would do better to consider the actual results of systems of parental choice that already function in other nations—and in ten Massachusetts cities.