I only missed one Friday because of an event (coupled with an ISEF affiliated science competition the day before) and one of my teachers freaked out that I was absent for so long. It was emotionally draining and caused so much tension between said teacher and I that we had to take it to the principal to sort out.
She refused to give me extensions while I was unable to do any work for her class. My grades weren't as high the ensuing two weeks.
Given all of this I would prefer to have Friday-Sunday competitions. I miss way too much school in the Thursday-Saturday model, and think I'd be too tired Sunday to do any work anyways. I tried to do most of my hw after we were eliminated on Sunday which worked (except for said teacher's class of course).
(s/o to those kids that helped me with my AP Bio homework
).