Based on the limited amount of SMPs that I have heard of, most start in the fall. The reason being they simulate med school curriculum, and thus classes go in a certain. Even if the classes were merely graduate (for MS/MA, PhD), then they would follow the same format as well. For example our pharmcology course here is a series of 3 classes. Each class is offered each quarter in a consequtive manner, thus you would not be able to take 3rd quarter pharm without taking 2nd quarter, and 1st quarter pharm from the previous quarters.