This article uses state-level achievement data to examine the academic progress of Arizona American Indian elementary public school students before and since the implementation of the No Child Left Behind (NCLB) Act. In most subjects and grades, American Indian students are making greater progress since the implementation of NCLB. Generally, American Indian students outpace all other major racial/ethnic groups. Compared to their White counterparts, however, American Indian students are most often either falling further behind or are not making sufficient progress to close the achievement gap. Most of the progress since NCLB coincides with changes to Arizona's state assessments and once data from a one-time test score spike are omitted, the achievement rates of American Indian students drop precipitously. The volatility of these results raises concerns about the integrity of state assessments in high-stakes accountability systems. Finally, recommendations are made to improve the NCLB large-scale assessment and evaluation provisions.