After learning English well in senior high school, it is easy to pass CET-4 by adding some CET-4 skills after entering the university, but this does not mean that senior high school English is equivalent to CET-4, and universities generally do not advocate freshmen to take CET-4 now, because after all, they still have to learn some college English content.
The prerequisite for taking CET-6 is to pass CET-4.
Don't worry if you don't learn English well in high school. Through college English learning, it is generally no problem to pass CET-4, and there are many students who pass CET-6. Language lies in listening, speaking and writing, which requires environment and exercise. This is something you can't finish learning!