Platonic crushes are also a thing.

You held someone in high esteem. They got grossed out by you and rejected you repeatedly for years. You are anxious and probably excited to no longer have them shunning you so adamantly.

I'd probably ask to talk, mention that you considered them a best friend and idolized them a bit, but then they shunned you for years and now you feel anxious to be around them and would like to finally hear their side in order to get closure.

Make sure that you mention you aren't after a friendship anymore and don't want anything from them, that you never coped with the ended childhood friendship and are just hoping that maybe a conversation about it can help you relax more around them in class, and that it's okay if they don't want to talk about it.