This answer deals exclusively with non-immigrant students; that is, students who are not residents of the United States and who are in this country temporarily. If a student who is not a citizen of the United States nevertheless lives in Iowa with his or her parents, the school district of residence is required to provide a tuition-free education to that student. This is true even if the parents of the student are in this country illegally. See Supreme Court's 1982 decision in Plyler v. Doe, 457 U.S. 202, 102 S.Ct. 2382, 72 L.Ed.2d 786 (1982).
A foreign exchange student is one who is sponsored by a program designated by the United States Department of State, Exchange Visitor Program and Designation Staff. These students generally are in the U.S. on a J-1 visa. Students whose residences are in another country who attend school in the U.S. and are not sponsored by an exchange program are here usually on an F-1 visa.