You first face the decision of whether to forbid the walk-out at all or to simply deal with the disruption caused by a walk-out. (This decision might depend on whether you are considering the disruption caused by a 17-minute walkout versus that of an all-day walkout). You then face the decision of whether or not to punish the participants. Note that a punishment must be proportional to the misconduct committed. Furthermore, if you decide to mark truant the students who participate in a walk-out, keep in mind that the punishment for them cannot be any more severe than the punishment for students who are truant for another reason.
Simply locking students into their classrooms in order to keep them from leaving may well be a fire code violation. Such a “lockdown” lacks the urgent “true threat” justification that a court might accept with regard to an active, dangerous incident in your building or near your location.
You should also consider that there may be another approach altogether. Given that we live in an age where there is much concern that young people don’t understand the Constitution or support free speech, punishing them for exercising it, even if the even if the Tinker decision gives school administrators that discretion, seems counterproductive. In the words of law professor Erwin Chemerinsky, “Schools cannot teach the importance of the First Amendment and simultaneously not follow it.”
This could be a teaching moment for your students and your community. In cooperation with students, parents, and teachers, you may wish to organize a town hall meeting in which all sides surrounding the political issue or debate are head. Newseum Ed’s Teaching Controversial Topics instruction guide provides tools and tips for educators on leading classroom conversations about sensitive topics.
You can also use this as an opportunity to educate your students about how the First Amendment works and how far their rights extend. You can start by introducing students to what the limits of free speech are, both inside of school and out of it, with discussion materials from Newseum Ed about what counts as a violation of the First Amendment and what you can and can’t say in school.