Filters are OK. The Supreme Court has said that libraries do not, as a general rule, violate the First Amendment when they use blocking software to limit Internet access. In fact, schools may be required by the Children’s Internet Protection Act, as a condition of receiving federal funds or discounted access rates, to use blocking software to prevent student access to obscene and pornographic material and anything else “harmful to minors.” [1]  That could be defined too broadly. No court has said so yet, but just as school boards can’t order books off the school library shelves just because they dislike their content, school libraries should not use blocking software to favor some nonobscene content or viewpoint over another, such as a filter that allows access to anti-choice websites but blocks access to pro-choice websites.

See the more general discussion of your right to Internet access ("Internet Activity") on school computers elsewhere in these materials.

[1] The Children’s Internet Protection Act is at 47 U.S.C. § 254(h)(5); it was upheld in a case involving public libraries and not addressing school libraries, United States v. Amer. Library Ass’n, 593 U.S. 194 (2003).