Is he hinting something or am I dumb?

No, if anything what he has done means that he does want to ask you! If he did not want to ask you then he would not bring it up around you as he would not want to put any ideas in your head. What I would do if you is to send vibes his to let him know that you like him and would like him to ask you. Remember, guys rely on getting these sorts of hints to guide them and to let them know how you are feeling so that they know whether or not to continue pursuing you. Doing things like making small talk where possible and giving him the odd compliment will go along way towards conveying your interest. Furthermore, if you get the chance to talk to him, try asking him questions that will get him to reveal his personality. In particular, the latter of those is really attractive to a guy as it shows him that you are interested in connecting on a personal level. Good luck and I hope this helps :)

Geez- I wouldn't go back to high school again for any money in the world! Life gets much better after high school-believe me. Now- you're in school and you're going to have a prom? Really? During COVID? If he's talking about the day after prom, it sounds like he's not asking you. But really- why would any guy go on about prom in Spanish class? Most guys don't really like prom, and they spend it lurking around the dance floor while the girls dance together. Next time he brings it up, suggest that you get a group of friends together to go- that's the most fun anyway. 

he might be hinting something

You're both just dumb. It's impossible to know if he's hinting something. Just ask him.