An underachieving middle school math teacher who never left home is forced to reconsider his life choices when his ex high-school sweetheart, now, an international movie star visits their hometown.

What Richiev said. As a result of his now-famous ex visiting town (inciting incident) what does he do, what action does he take?

Things like, 'force to reconsider his life choices' don't work well in loglines.

You are better off telling us what 'action' he takes instead.

Take High Fidelity, a movie with John Cusack. You could say "After his girlfriend dumps him an eccentric record store owner is force to reconsider his choices in life"

Or

You could tell us what action the character takes. "After his girlfriend dumps him, an eccentric record story owner visits his past girlfriends to discover what when wrong.

Action; he visits past girlfriends.

So in your story, when his high school sweetheart comes to town and he reconsiders his life choices, what action does this prompt, what does the character do? That should be your logline.

Hope this helps, good luck with this!