What is the Tinker Test and how does it apply to free speech in school?

The Tinker test is used to determine when public school officials may discipline students for free expression. It is the leading test used in student speech cases including off-campus online speech.
The Tinker case comes from public school students in Iowa wearing black peace armbands to protest the Vietnam war. The students were suspended after a no-black armband policy was enacted. The suspension was challenged in court where the students lost in the lower courts. However, the Supreme Court ruled in their favor stating there was no finding that engaging in the forbidden conduct would materially and substantially interfere with the requirements of appropriate discipline in the operation of the school,"
In 1972, the Tinker test was used to rule that a public school could prohibit the wearing of the Confederate flag.
A 2015 decision ruled against students that posted a rap video online that criticized two teachers which shows the Tinker test still applies even if the content is online.
In 2021, the Supreme Court ruled in favor of a student that posted a vulgar Snapchat post off campus which shows that a school’s interests are lessened when students engage in behavior off campus.
Works Cited:
https://www.mtsu.edu/first-amendment/article/1584/substantial-disruption-test