Graduate programs (in all disciplines, not just nursing) tend to vary greatly from one another. Different schools
offer different specialties and design those specialties in accordance with the interests and expertise of the faculty and the needs of the school.
For example ... at one school, there may be a relatively small number of students. So, they can't offer a million different specialty tracks each with unique courses focusing on just that specialty. Such a small program would offer several "core courses" on general topics that all students would take and only a few specialty courses. On the opposite end of the spectrum, a huge program has plenty of students to fill many different classes. So they don't need to save money by requiring lots of generalized core courses. They can have more specialty courses because they will have enough students to fill those courses.
A lot of factors (such as size) influence such decisions.
Also ... philosophically, faculty differ on what they think is most important. The faculty at one school might think it is more important for an education specialist to learn a lot about education -- and figures that the nurse can learn whatever physiology, etc. she will need when she needs it. Not every nurse NEEDS advanced physiology, pharmocology, etc. (I haven't needed that kind of information for years.)