attending superday at BB even though accepted offer at another bank?

I know this isn't ethical, and personally have turned down some other interviews/superdays in AM and S&T already at lesser tier firms.

I already accepted a summer analyst position in S&T at a lower tier bank, but its presence isn't as large in the US than abroad, but I'm very grateful and talked to a lot of people there - including an MD in IB who introduced me to the firm. I was a little annoyed because I had to accept in five days without getting a chance to attend another superday that I ended up not going to because rejecting the offer was too risky.

Today I got invited to a superday next week at Credit Suisse that I am highly considering going because it is the most prestigious compared to other invites I've gotten and turned down. The recruiting seems fast-tracked as if they are filled someone else who reneged, because it is really late in the process I think.

The issue is I have midterms next week and one happens to be the exact time as the superday. I already emailed saying I cannot attend because of the conflict. Shoud I just email again to say I cannot proceed in the process?

I would love to level up to bulge bracket, but not sure if it is worth the time and since I already build connects at the firm I've accepted an offer for. But also I don't want to miss out on this opportunity to be able to work at CS if I get the offer. I've read other threads and some people say to go because it can't hurt, but I have a special case where I physically can't due to the midterm.