The demographics of U.S. elementary and secondary schools are changing rapidly as a result of record-high immigration. These demographic shifts are occurring alongside implementation of the No Child Left Behind (NCLB) Act, the landmark 2002 federal law that holds schools accountable for the academic performance of limited English speaking children and other groups that include many children of immigrants. This report explores how immigration is changing the profile of the nation's elementary and secondary student population during this era of reform. The report begins by describing children of immigrants and limited English proficient children. Next, it discusses children of immigrants in low-income families--another protected group under NCLB. After that, the report examines how family income and parental education interact with linguistic proficiency and isolation. Finally, the report describes characteristics of children of immigrants who fall within the major racial and ethnic reporting groups mandated under NCLB--Latino, Asian, and black students--and draws comparisons among children with parents from different countries. (Contains 7 tables, 25 figures, and 30 notes.)