Limited Public Forum -- Specific Legitimate Purpose

school mailboxes, -- limited to mailings from "organizations that engage in activities of interest and educational relevance to students” (Perry Ed. Assn. v. Perry Local Educators' Assn);

public university could limit the use of its facilities by reasonable regulations compatible with its mission of education (Widmar v. Vincent)

school board meetings limited to specified subject matter (Madison Joint School District No. 8 v. Wisconsin Employment Relations Comm'n)

school mailboxes, -- limited to mailings from "organizations that engage in activities of interest and educational relevance to students” (Perry Ed. Assn. v. Perry Local Educators' Assn);