Go directly to the Student Handbook.
1. IB permits overseas credit, but the program of study must be approved beforehand by the Head Tutor.
2. Cross-registration. To take courses for credit at MIT or elsewhere, students must make a compelling case to the senior tutor that the equivalent is not available at Harvard and that the level is appropriate to Harvard.
3. Harvard Summer School. These courses are typically not considered appropriate for credit in IB, but petitions (to the Head Tutor) may sometimes be granted.
AP courses do not count for credit in the IB concentration. However, AP courses may allow you to enroll in higher level courses in Math, Physics and Chemistry to satisfy requirement (d).