Have you ever noticed that even though you and your friend have different history teachers, you are both learning the same thing? That is because of the uniformity, or sameness, of the curriculum. All teachers have to teach the same thing.
Think about the word uniform. When you see police officers or students in uniform, it makes them all kind of look the same. If things don't change, you can say there is uniformity. Uniformity can be a good or a bad thing. A uniformity in TV shows would be boring. Variety here is much better. On the other hand, you would like to see uniformity among medical schools, so you know all doctors are qualified.