She's exactly the kind of character/person that falls for an older guy who ends up needing to let her down firmly but compassionately. It'll hopefully help her focus on enjoying her youth as a child instead of rushing things.
They've been setting up this arc for her with how she acts a little more "mature" than the others, and mentioned not liking boys her age. Many of us had our own teacher crushes growing up, and this author hasn't sexualized any of the cast so far at all. I trust that it won't be a taboo development, and I don't think it's a weird story beat, personally.
Ironically, this is something that young teacher will need to get good at navigating, because Lulu ain't gonna be the last girl to get a crush lmao