In Tinker v. Des Moines Independent Community School District (1969), the United States Supreme Court famously held that public school students do not “shed their constitutional rights to freedom of speech or expression at the schoolhouse gates.” Recognizing that these rights are necessarily limited, the Court added that school officials retained the authority to punish expression that “would materially and substantially disrupt the work and discipline of the school.” In that decades that followed, judges applying Tinker have used the case to dramatically limit student speech rights. This result was achieved through two distinct argumentative moves. These decisions subtly broadened a legal standard that originally required actual disruption to include student speech that had the potential to disrupt. At the same time, these decisions delegated the authority to characterize expression to school officials. Using this power to define, it was easy for administrators to repress student speech by asserting that the possibility for disruption was sufficient to satisfy the “material” and “substantial” criteria set out in Tinker. Taken together, these simple definitional moves allowed judges to transform a landmark decision originally intended to protect student speech rights into a powerful precedent that can be offered to restrict student speech.