The black-white educational achievement gap -- so much discussed for so many years -- has already been closed by black students attending New York City's charter schools. This might be expected to be welcome news. But it has been very unwelcome news in traditional public schools whose students are transferring to charter schools. A backlash against charter schools has been led by teachers unions, politicians and others -- not only in New York but across the country. If those attacks succeed, the biggest losers will be minority youngsters for whom a quality education is their biggest chance for a better life.