The Navajo Language Immersion School--"Tsehootsooi Dine Bi'olta'," to use its Navajo name--made adequate yearly progress in all subgroups under the No Child Left Behind Act during the 2005-2006 school year because "the teachers know exactly where their students are in terms of data." The K-8 school with 235 students in the Window Rock Unified School District, on the reservation of the Navajo Nation in Arizona, draws on both Navajo tradition and modern accountability tools to improve student achievement. Educators at the Navajo-immersion school, where 71 percent of students are from low-income families, have embraced state academic standards and federal accountability requirements under the law through a school improvement plan. The school also teaches standards for Navajo culture published by the tribe and operates a program intended to teach literacy and improve oral proficiency in "Dine"--the word Navajos use for their people and language. Kindergartners and 1st graders receive all instruction in Navajo. Lessons in English, including reading, begin in 2nd grade and occupy an increasing amount of class time with additional grades. By 6th grade, children receive half their instruction in each language. There is no question that school leaders see the infusion of native culture and language as a key to its success.