I see you have a command of semantics but not of the issue. The language that is to be spoken in school - during class, recess, in the halls, bell to bell - is English. The proposition that came into law seems pretty clear on the matter. And if not to some, the principal, the person that runs the school, has made it clear for them: Speak English.
That's not too hard to sort out is it?
In the class, yes. But outside of the class it is not your or state business.
What if children want to practice a little French for the French class? Ot if they want to say a prayer in Latin or Hebrew? Or if friends or siblings like to speak their home language, or American Indian children want to speak their tribal dialect? Will you punish them, how? And what will you achieve but doing this?