Should a TeamMembers table have a relationship with the Student Table or the Enrolment Table?
I would have assumed that one team can have many users and one user can be part of many teams thus creating a new junction table, Users_Team. From there I would have related users to Enrollment or user_team to enrollments depending on business logic. Am I right in assuming that enrollment will contain recrods such as Maths, Science, Art etc...? 

Does it make sense for a user to be enrolled in maths as a individual, and also as a team?

From my understanding, I would drop that TeamMembers table.