Support for student expression and First Amendment attitudes were measured among Missouri high school principals (n = 86). Findings demonstrated that the third-person effect was a significant predictor of these attitudes. The more principals perceived mass media to affect others over themselves, the less supportive they were for student free expression rights, particularly with regard to support for online, off-campus student speech. In addition to applying communication theory to a largely atheoretical field of scholarship, this research helps suggest several directions for future research to better understand restrictions on student speech. (Contains 3 tables and 30 notes.)