They don't need chromebooks in schools, my kid uses YouTube kids at home (that doesn't include shorts), teens will have their own phone usually, and youtube is already a popular place for them to go, discovering YouTube shorts (if they haven't already), is easy.

But ya, if a teen is otherwise cut off from devices besides the ones they get from school, then you could see that as a weak point, although I don't think that applies to a significant portion of families. For the ones that it does apply to, they probably have bigger problems to worry about than TikTok being banned.