That would fall under my "school is a Marxist hellhole" exception, as "the district is trying to ruin the school when it might have been slightly okay."
I'm a fan of self-defense, but I don't know enough about the particular situation to reach a conclusion. However, I'm a bigger fan of common sense, which says that students skipping school will do absolutely nothing to un-dead the dead person, or to evaluate the facts so that the proper authorities can reach a correct conclusion on what to do going forward.
The only legitimate purpose of a walkout is to provide attention to a potentially unjust situation.
This story has way too much attention as it is.