The free speech case so complicated it seems to have stumped the Supreme Court

Mahanoy Area School District v. B.L, which the Supreme Court heard on Wednesday, is a tough case. And it’s not tough because it presents the kind of politically toxic questions that often cause the justices to retreat into their partisan corners.

Members of the Court from across the political spectrum spent Wednesday morning struggling to determine when a school district should be allowed to discipline students for speech that they engage in when they are not at school or engaged in any kind of school-sponsored activity. The question has become...