I am going to suggest a different approach...
1) Ask yourself what your team's vision is. If your team doesn't have a vision of what it wants to be and do then start by forming one.
2) Take the time to communicate with each of the members (student and mentor) about what strengths they can bring to the table to help the team obtain it's vision. This is time consuming but important since it means a leader will be investing face-to-face time with each individual member.
3) Decide as a leader if an individual is worth the resources to develop into a productive team member.
An old adage comes to mind, "One in the hand is worth two in the bush." You have people regularly attending meetings, why not invest resources in them instead of assuming you can recruit others to fulfill your team's vision?
Every so often there is a thread topic similar to this. Generally it is not a case of the students not being active participators, it is a direct result of the team's leadership. Followers can only grow to be equal to their leader. For further growth the leader must grow as well or the follower must find a new leader.
I highly recommend reading any book by John C. Maxwell. You may find it useful to start with
this one.