Unless a student's speech would disrupt the educational process, students had a fundamental right to speak their minds. Even if the school disagreed with the topic at hand.
sources:
Tinker v. Des Moines Independent Community School District
Students also have freedom of speech and the freedom to express their ideas, meaning that the school can not prevent them from promoting the use of illegal drugs at school. They can only not allow the use of illegal drugs, not the promotion of illegal drugs.
Tinker is without basis in the constitution and the history of public education suggests that the First Amendment does not protect student speech in public schools.
sources:
Tinker v. Des Moines Independent Community School District
(Justice Thomas)