Immigration and migration to New York City (NYC) collectively create a dynamic population of students. In this brief the authors use a decade of detailed, longitudinal data on NYC's 1st-8th graders to explore both the "stock" of students enrolled and the "flow" of new entrants in each academic year. Together, these paint a portrait of how newly entering immigrant students shape the ever evolving diversity of NYC public schools. New York City's elementary and middle schools receive between 20,000-30,000 new students in grades 2-8 every year. These students come from all over the world, speak over 175 different languages, and differ from the stock of students previously enrolled. Although the composition of new students varies annually, the variation manifests itself in both predictable and surprising ways. The research consistently shows that roughly half the new entrants in any year are native-born and that the flow of native-born students differs from the flow of foreign-born students, particularly in language skills and exposure to English at home. In the early grades, new entrants are disproportionately native-born, but as students age, the flow becomes increasingly foreign-born. Therefore, disentangling these groups and being more precise about "which" immigrants or "which" new students are examined is important in determining policy interventions. Four questions are addressed in this brief: (1) How many new students are there? (2) How have immigrants changed in the past decade? (3) Do new immigrant students lag behind native-born entrants on standardized exams? and (4) With whom do the new entrants go to school and are their schools different? This brief is intended to provide insight into this important group of newly entering students and to shed light on the variation in this population between nativity groups, over time, and across grades. Two supplemental tables are appended: (1) Total enrollment in NYC public schools; and (2) Foreign-born population in NYC.