'Holiday' during term time - one day??

Ok, so, it's not necessary for me to do this, but I wanna know if I can. And I'm asking here because all the stuff about having days off in sixth form are about week long holidays and this is just one day. ('Why don't you fake being sick?' I would feel ABSOLUTELY awful about lying, you wouldn't believe.)

I have a event in February in London (I'm about three hours away) that spans three days: Friday, Saturday, Sunday. Friday is a tester day: Like I said, it's not the end of the world if the correct answer to this is 'No, you can't, c'est la vie', but I'm asking because the ticket spans the entire weekend, like a friend said, it's better to get your money's worth. Plus it would make our situation a tiny bit easier.

I have three lessons on this day: Sociology (Of which my teacher leaves detailed resources online for those who have missed lessons) and two study periods. I can catch up on Sociology, and I can make up for the study periods I missed in half term in my own time.

Is this worth bringing up to my head of sixth form as a consideration? I'm aware how much of a stupid question this is and it probably seems selfish and 'first world problems' as hell even if I'm not intending it to sound that way, I apologise. I just overthink so much. But if this is possible for me to do, It'd help me out so much.

(My attendance is pretty good apart from the three or four times a year my pathetic excuse for an immune system screws up and even then I usually manage to come in)

Honestly I would probably say go. It's one lesson (realistically speaking) and you're gonna be able to catch up relatively easily. I'm assuming it's not in any way educational and you can't play it off as something you're doing for your personal statement or anything? Just ensure you catch up and it'll be fine if your attendance is otherwise good!

its a convention: i cant play it off as educational at all: if i did drama, perhaps i could call it extra circular since ill be doing something onstage, but i dont, so it wont play into my studies in any way.

I mean it's ultimately up to you, I would say you're doing a performance and it would be really helpful if you could go down early to set up/practice on stage etc.
The other option is, is your sociology lesson first? You could go to that then leave before the study periods in order to not miss any teaching time. As you say you can catch up your study periods over half term!

my sociology lesson is fourth period. after one study. that idea might work