If you TW in class, every student receives it and gets to potentially benefit from it, and you can…

If you TW in class, every student receives it and gets to potentially benefit from it, and you can provide it immediately before the potentially triggering content arrives, rather than providing a blanket warning that it will come up at some point that day. It makes more sense to provide a public TW for any trigger that might be relevant to other students who have decided to not come forward about having triggers (so, the really common ones — sexual assault, murder, gore, blood, etc, but also eating disorder related content like calories and weight talk and food). It might be more practical to use a private TW for very specific/rare triggers that you are unlikely to use once the student triggered by that content is no longer in your class. But generally I default to public.