In K.A. v. Pocono Mountain School District, 710 F.3d 99 (3d Cir. 2013), the U.S. Court of Appeals for the Third Circuit decided, as a matter of first impression, that the advertising material of third parties constitutes "student speech," if distributed by a student in the public school.
Untangling Student, Third-Party Speech in Public School
The Legal Intelligencer
June 27, 2013