Curriculum theory basically teaches us that learning takes place in school based on a number of curricular units such as mathematics, literature, history, geography, biology and other subjects. However, we often see how in schools these curricular units go through some modifications over time, it is logical to think that nothing over time should remain the same, since suddenly a curricular unit is demanded for a specific time, but over time it is no longer very useful.
It is also important to mention that not all curricular units have had a changing rhythm throughout their history. For example, subjects such as mathematics, history, geography, literature and pure sciences have existed as curricular units in many schools and I believe that they will exist forever.
On the other hand, there are other curricular units with which tests are carried out to evaluate their usefulness based on the requirements and demand of students' knowledge, but then they have to be modified and adjusted to new demands.
The curricular theory can have an approach based on the exploration and form of the contents that must be taught in the educational environment, not only in a particular stage but in all stages of education, for example at university level it is very important that these curricular units are being checked since the future professional needs to be innovating their knowledge to the current times.
Sometimes I think of the useful element in education at all levels that can help to replace at a certain time the model of curricular theory, it is at that moment that I think of the insertion of professional work in an early university education, so that instead of being governed by a curricular model we are governed by a practical model in which teaching and learning by doing is taught and learned.