This paper will begin with an overview of the Mahanoy Area School District v. B.L., which ruled on the constitutionality of students' freedom of expression on the Internet, in Chapter I. In Chapter II, we review the major U.S. Supreme Court decisions on student freedom of expression in public schools prior to the Mahanoy decision, and then examine the relationship between the Mahanoy decision and these precedents. Chapter III discusses the doctrine of "in loco parentis" as applied by Justice Alito, who wrote the opinion and concurrence, and Justice Thomas, who wrote the dissenting opinion.