The actual number of classes is going to depend on the school. Are they systems based? Do they integrate clerkships during the first year? Do they have some kind of leadership and/or patient interaction coursework that underlies the sciency stuff? Are they 18 month or 2 year pre-clinical? Are they osteopathic (OMM classes added in)? And so on.
I have no experience with going through medical school, however I have heard that course-load wise it is about the equivalent of 20-25 credits of upper division science courses per semester pre-clinical. The content should ideally be the same across schools, with some differences about the availability of specialized electives/support for students.