Lock step or unstructured? Both have their advantages.
Some MBA programs are designed so that during the first year (or more), all students in the program take classes in "lock step," that is, they all take the same courses at the same time. This arrangement is most amenable to the formation of student study groups in which members may experience the dynamics of working together in a long-term group, and develop strong personal and professional ties to other group members.
On the other hand, an unstructured approach allows a student the freedom to determine which courses to take, and when. This may be most appropriate for students who, due to financial or time constraints, cannot commit themselves to a group.