The question of the necessity of school punishment was raised, but not satisfactorily answered, in an exchange some time ago between John Wilson and James Marshall. Wilson argued that social interaction in schools must be governed by rules and that rules only exist if violations of them are normally punished. Marshall objected that there are some rules whose existence plainly does not depend on punishment of violations. Here I revisit and try to resolve the disagreement between Wilson and Marshall. I contend that, while it is not true of rules per se that they must be backed by punishment, there is an important subset of rules that do require this backing, and that subset includes at least some of the rules governing social interaction in schools.