Oooh!! interesting...I shall answer as best I can!
Slimeberry - if he is still self aware of his existence in this case, then he'd totally just ignore any studying all together, not even entertaining the group chat and just ignoring any text sent to him- but if he isn't aware, he'd probably just slack off most of the time and would rather send the group chat memes at 3 am the night they are presenting lol
Accendio: He would probably get done first before anyone else, Accendio would be the type to help with everyone no matter the subject- even if they aren't good at said subject, mother of the group.
Vivi: Surprisingly, Vivi is the type to do studying last second but we can all probably guess why, they are a prophet and just know all the answers no matter the subject, so they would rather meditate the whole way through and just wait till everyone else is finished.
Dopple: He is probably the one that needs help the most out of this squad, Accendio is his emergency contact for studying lol
Hydra: Is also a slacker but not for the same reason Slimeberry is, Hydra is just...really insecure about anything he does, so instead of studying- he'll just stare at the paper from a dark corner and just second guess every answer- but if he is motivated to do it, then he will most likely ace it.
Xrandi: Okay...I am so sorry but Xrandi is the straight A student who is somehow really incapable of being helpful or smart- okay, Xrandi is extremely smart obviously cause they are an alien but...in a modern AU, I feel like they'd be able to answer the digits of Pi perfectly but cannot explain it at all, even if they tried to answer- you'd be just as confused as you were earlier because they'd explain it poorly lol
Irise: I feel like he wouldn't really need to study much, she'd just kinda wing it and somehow get 100% on the paper- and in class, they would literally be daydreaming while writing on the paper- not even paying attention to the question yet somehow get it perfectly- though, Irise would totally help you if you asked! if you wanna get a perfect 100% everytime on a test, just ask Irise or Vivi!
Sequoia: Had the butlers to do it for him, she will get a little prideful about it when their score is said allowed lol
Kit: Oooh...okay, I'm sorry but Kit is the type to totally get every question wrong yet still try to help everyone he can with the test/studying- they wouldn't even be upset about the low score half the time either lol
Silver: In a modern AU, Silver is the type of person who is totally done with the test in the blink of an eye. They would also be correct 100% of the time too- but if they somehow aren't...let's just say the teachers would be too terrified to even tell them that.
Heno & Kumo: These are the troublemakers, they don't say much in the groupchat cause they are too busy being pranksters together (modern au obvi), in class during the test, they are the types to be talking to eachother the entire time and not do a single thing on the paper- Heno would get like 10 questions in and Kumo would get one question in but both completely stop working to just talk with eachother lol
Karakasa: He is the only person who is completely silent and doing the test properly, like- this man will write in perfect cursive the entire time and not slip up once, but also...Karakasa is the type of student who is gone for most of the days and usually returns on like a random rainy day. (always has an umbrella)