Recently, much attention has focused on the number of schools in the nation failing to make adequate yearly progress (AYP) in raising student achievement under the No Child Left Behind Act (NCLB). The Obama Administration has projected a dramatic increase in this number as 2014--the year when 100% of students are expected to score proficient on state tests--draws nearer. Testifying before Congress this March, Secretary of Education Arne Duncan warned that "we did an analysis which shows that next year the number of schools not meeting their goals under NCLB could double to over 80 percent--even if we assume that all schools will gain as much as the top quartile in the state. So let me repeat that: four out of five schools in America may not meet their goals under NCLB by next year" (Duncan, 2011). President Obama reiterated this warning in a March 14 speech on education (Obama, 2011). The Center on Education Policy (CEP), an independent nonprofit organization, has been monitoring national AYP data going back to 2005. This spring, CEP updated the four-year trends described in its December 2010 AYP report by adding a fifth year of data on the estimated number of schools in the nation and each state that did not make AYP in 2010, based on tests administered in 2009-10. Here are the main findings: (1) An estimated 38% of the nation's public schools did not make AYP in 2010. This marks an increase from 33% in 2009 and is the highest percentage since NCLB took effect; (2) In 12 states and the District of Columbia, at least half of the public schools did not make AYP in 2010. In a majority of the states (39 and D.C.), at least one-fourth of the schools did not make AYP; and (3) The percentage of public schools not making AYP in 2010 varied greatly by state, from about 5% in Texas to about 91% in D.C. Estimated percentage and number of schools in each state that did not make AYP based on test results for 2010 are appended. (Contains 1 figure, 1 table, and 1 footnote.) [For the companion report, "State Policy Differences Greatly Impact AYP Numbers. A Background Paper from the Center on Education Policy," see ED518992.