Within assigned group or groups?

Hi. Please tell me which is correct. I think both are correct, although no. 1 makes it clear that the indicated achievement is for individual groups with a student belonging to a group, not multiple groups. I hope I've written what I wanted to say clearly (not sure, though). Anyway, thank you in advance for your help.

It focuses on students' academic achievement within (1) their assigned group / (2) their assigned groups in various disciplines.