Florida's A+ voucher plan is improving accountability and raising test scores, according to Harvard University researchers. Under the Florida A+ Plan, students in consistently failing public schools can use vouchers to switch to private schools. Using test scores of 900,000 students for 2002, 2003, and 2004, Harvard researchers find that "students in schools that received their first 'F' grade in the summer of 2002 scored 4 to 5 percent of a standard deviation higher the following year than did students at comparable 'D' schools not subject to the voucher threat." African-American students, low-income students, and students with the lowest initial test scores showed some of the strongest gains. Significantly, researchers find that the choice provisions in Florida's A+ Plan are better at promoting student achievement gains than provisions in No Child Left Behind.