After weeks of homework assignments and preparation, the chief executive officer at the Boys & Girls Clubs of Lanier is finishing up a week of one of the most rigorous and challenging intellectual bootcamps at one of this country’s most revered institutions of higher learning. For the past week, Steven Mickens and a select group of other Boys & Girls Clubs executives from every region of the United States have been learning at the Harvard Business School Executive Education. Mickens and company are training to confront organization-wide challenges and problems through strategic solutions they’ve had to brainstorm.