.. this case doesn't cross into that case's precedent. That case relied on Morse v Frederick which limited the scope of speech that advocates illegal activity.
Wearing a flag does not promote / advocate illegal activity.
Tinker v. Des Moines Independent Community School District is the appropriate precedent-
The District Court recognized that the wearing of an armband for the purpose of expressing certain views is the type of symbolic act that is within the Free Speech Clause of the First Amendment. See West Virginia v. Barnette, 319 U.S. 624 (1943); Stromberg v. California, 283 U.S. 359 (1931). Cf. Thornhill v. Alabama, 310 U.S. 88 (1940); Edwards v. South Carolina, 372 U.S. 229 (1963); Brown v. Louisiana, 383 U.S. 131 (1966). As we shall discuss, the wearing of armbands in the circumstances of this case was entirely divorced from actually or potentially disruptive conduct by those participating in it. It was closely akin to "pure speech" <393 U.S. 503, 506> which, we have repeatedly held, is entitled to comprehensive protection under the First Amendment. Cf. Cox v. Louisiana, 379 U.S. 536, 555 (1965); Adderley v. Florida, 385 U.S. 39 (1966).
First Amendment rights, applied in light of the special characteristics of the school environment, are available to teachers and students. It can hardly be argued that either students or teachers shed their constitutional rights to freedom of speech or expression at the schoolhouse gate. This has been the unmistakable holding of this Court for almost 50 years. In Meyer v. Nebraska, 262 U.S. 390 (1923), and Bartels v. Iowa, 262 U.S. 404 (1923), this Court, in opinions by Mr. Justice McReynolds, held that the Due Process Clause of the Fourteenth Amendment prevents States from forbidding the teaching of a foreign language to young students. Statutes to this effect, the Court held, unconstitutionally interfere with the liberty of teacher, student, and parent
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The District Court concluded that the action of the school authorities was reasonable because it was based upon their fear of a disturbance from the wearing of the armbands. But, in our system, undifferentiated fear or apprehension of disturbance is not enough to overcome the right to freedom of expression. Any departure from absolute regimentation may cause trouble. Any variation from the majority's opinion may inspire fear. Any word spoken, in class, in the lunchroom, or on the campus, that deviates from the views of another person may start an argument or cause a disturbance. But our Constitution says we must take this risk, Terminiello v. Chicago, 337 U.S. 1 (1949); and our history says that it is this sort of hazardous freedom - this kind of openness - that is <393 U.S. 503, 509> the basis of our national strength and of the independence and vigor of Americans who grow up and live in this relatively permissive, often disputatious, society.
In order for the State in the person of school officials to justify prohibition of a particular expression of opinion, it must be able to show that its action was caused by something more than a mere desire to avoid the discomfort and unpleasantness that always accompany an unpopular viewpoint. Certainly where there is no finding and no showing that engaging in the forbidden conduct would "materially and substantially interfere with the requirements of appropriate discipline in the operation of the school," the prohibition cannot be sustained. Burnside v. Byars, supra, at 749.