Some students study better alone but there are some advantages to studying in a group.
By studying together, you can compare notes to see if you missed something important, you can build sets of “flash cards”, and you can make and give each other sample test questions.
Everyone in the group must insist the group stays on task and does not turn into a hindrance instead of a help.
You will probably have different members of your study group for different classes. If your study group for each class is the same people, it is probably a social group, not a study group.
The study group should not take the place of asking the instructor for help.