First, as a leader, you can delegate work to other people and tell them that you have a lot of schoolwork to complete.  If the lack of time is going to be an ongoing problem, I think you should step down from your leadership position and concentrate on your schoolwork.  You can still play an integral role by advising your organization’s leaders.  When firms hire, they look at your school, your grades, and, finally, your involvement in organizations.  I think you should concentrate on being well-rounded, rather than exemplary in one area (organizations) and failing in another (schoolwork).