I started HS in NC, and Seniors did not skip, the school I attended allowed seniors to be exempt from finals if they had perfect attendance. So no senior ever missed a day unless they had no choice.
Then I moved to PA in my sophomore year and was exposed to the entire concept of Sr Skip Day, which made me realize the precious HS was run by far smarter people than the one I transferred into.
I taught in an urban high schools for much of my career. Most of the honors kids had darn good attendance, except on skip day (in my school, it was junior-senior skip day). I disliked that day, as it made something wrong seem just fine.
So skip day was my bonus points day. Show up, and do some relatively easy bonus work. Apply it to your grade. And since I taught difficult subjects (chemistry and physics), those bonus points were often very much needed.
Most of my honors students showed up. They got their extra credit. Then they skipped right after my class. Oh, well. I tried.