There are two reasons: first, the knowledge points learned are not commonly used. If these knowledge points are remote and isolated, you don't have to worry too much about making mistakes again. Look through the books and you can do it again. Second, there is something wrong with your study method. It is likely that you are memorizing. This is a big problem. Rote memorization can still be effective for junior high school, but it is completely abolished for senior high school. In this case, you need someone to guide you to change your learning methods, and change is often painful and even tortuous, so you need to face many problems and break through many difficulties.

Tell your parents about this situation. If they can't solve it, they still complain that you are stupid, or "forgive" you with the useless "cleverness" of learning, then your parents are seriously dereliction of duty and incompetent. You need to break through the thinking influence brought by your parents before you can put down the burden they bring you and move forward lightly.