I noted a while back that Justice Thomas in many ways resembles Justice Hugo Black, who served on the Court from the late 1930s to the early 1970s. Justice Black was mostly seen as a liberal Justice, and Thomas as a conservative, but both shared a distinctive style that sometimes made them mavericks: Both generally took the view that constitutional provisions should be interpreted the way they were understood when the provisions were written. Both preferred clear, bright-line rules to tests that required more judgment in their application. And both were much more willing than their colleagues to reconsider settled precedent.
This is particularly clear in Justice Thomas's concurrence in the K-12 school speech case, Morse v. Frederick: He was the only Justice willing to reverse Tinker v. Des Moines Independent School District, the 1969 case in which the Court first expressly held that government-run K-12 schools generally may not restrict student speech. (The flag salute case, West Virginia Board of Education v. Barnette, held in 1943 that schools may not require students to salute the flag; but as of Tinker, it wasn't clear whether Barnette was limited to the unusual circumstance of compulsory affirmation of belief.) He rested most of his argument on what he argued was the original meaning of the First Amendment, as applied to the states through the Fourteenth. And he also stressed that the Tinker standard, coupled with the modifications added since then (including by the majority in Morse itself), was too subjective to be a workable and principled rule of law.
And interestingly, in this case Justice Thomas's bottom line as well as his decisionmaking style matched Justice Black's: Justice Black was the one Justice in Tinker who would have held that government-run K-12 schools have a free hand in restricting student speech.