New Mexico's Every Student Succeeds Act state plan set the goal for all English learner students to attain English proficiency within five years. The Regional Educational Laboratory Southwest English Learners Research Partnership conducted this study to better understand progress toward English proficiency among American Indian English learner students. The study examined two statewide cohorts of American Indian students identified as English learner students at initial kindergarten entry in 2013/14 or 2014/15 in New Mexico public schools. The study found that most American Indian English learner students were not reclassified as English proficient within five years. Similarly, most American Indian English learner students did not meet grade-level standards on New Mexico state assessments in English language arts and math in grades 3 and 4, regardless of whether they attained English proficiency and were reclassified within five years. However, considerably higher percentages of American Indian English learner students who were reclassified as English proficient met grade-level standards in both English language arts and math compared with students who were not reclassified. Finally, students who attended a school with a bilingual multicultural education program (BMEP) for at least four years were reclassified as English proficient and met grade-level standards on state assessments in English language arts and math at higher rates than students who never attended a school with a BMEP. Staff at the New Mexico Public Education Department, district and school leaders, and teachers can use the findings from this study to determine how best to support English language development among American Indian English learner students. [For the Study Snapshot, see ED618963. For the Appendixes, see ED618964.]