Curriculum design is about how a person envision what a curriculum should be. There are several standard models of curriculum design. One of the most prominent is the subject-centered design.
The subject-centered designer divides the curriculum into nice and neat subjects such as math, science, history, literature, etc. This structuring of the disciplines is for practical reasons. It organizes the curriculum into basic concepts that are combined based on what they have in common. The essential knowledge of each area is gathered together to be taught to students.
Where the division of the curriculum stops depends on its purpose. Any expert in education knows that subjects overlap and the division is often arbitrary. In addition, every subject can be further divide into smaller parts. For example, English can be broken down into writing, reading, speech, grammar, and more.
A major criticism of this design is the lack of integration or horizontal articulation. The learning is compartmentalized and the students often never see the connections across subjects. In addition, the subject-centered design does not take into account the needs and interest of the students. The textbook is made by experts in the field who already know what knowledge and even experiences a child requires.
Despite this, the subject design is by far the most popular approach. It is easy to do and practical. It’s appropriateness needs to be left to the educator who is trying to help their students.