I am looking at #Stoat (formerly #Revolt) and #Hubzilla as alternatives to Google Chat and Discord.
Stoat is more like discord in appearance and probably would feel more familiar for those users, but it's also very 18+ forward for a school project to coalesce on and it's not actually fedi, i think? (Their support is a bluesky channel, which I'm not going to join)
Hubzilla doesn't have a dedicated app, which i think people would like, and I'm not sure it does chatrooms.