If your child is interjecting with an observation that is clearly topical, then I'm at a loss to understand what, precisely, the teacher is trying to fix. Is being engaged a problem?

It so happens that DD8 is homeschooling, and DW has punted social studies to me. DD makes interjections like this all the time, and I handle it by laughing and saying, "Good point," and moving on... unless it happens to be an interesting line of digression, in which case, we explore it.