The statement that best describes a time when the Supreme Court decided that a Texan exercised the right to free speech is:
when a group of students wore black armbands to protest the Vietnam War.
This refers to the landmark case Tinker v. Des Moines Independent Community School District (1969), in which the Supreme Court ruled that students do not lose their First Amendment rights to free speech when they enter school property. The case involved students wearing black armbands to protest the Vietnam War, and it established significant precedents regarding student speech rights.