honestly i have the same issue TT
this isn't much advice, just letting you know that you're not alone. I thought that going to sixth form would be fun because i come from a very small high-school. so I was looking forward to making new friends, and I even forced myself to talk to people first and joke around a little, even though i have anxiety. For some reason, it feels like people are more comfortable/ put in more effort with others?? im honestly exhausted.
Honestly, giving u my own advice that i keep telling myself, give it a few more weeks - keep trying but don't drain yourself out. Like make small talk, if they don't reciprocate then that's the end of the convo.
SIDE "RANT": the two girls on my table in my sociology class are SO boring, the only thing they talk about is how much they don't wanna be there PLUS they only make effort w each other even tho i sit between em. (Like they legit do not speak to me - but they dont know each other from skl or anything) makes me dread soc sm.
Anyway, goodluck on making friends i hope you find someone ^^