Naven
Answers
How do you make a group chat for a school project?
Use something that works on a school device. That rules out anything requiring an install, and usually means a browser-based tool — Naven, or whatever the school itself provides.
The common failure is choosing the app everybody uses at home and discovering that half the group cannot open it at school. School devices forbid installs and often block the popular messengers by domain.
The second consideration is phone numbers. A project group is classmates rather than close friends, and a platform that requires numbers distributes everybody's to everybody.
A Naven group is made by naming it and adding people by email address, and it runs in the browser on a managed Chromebook.