1. What you learned at school is not only the knowledge itself, but also the learning methods. For a truly creative person, the latter is useful for life.
2. School education should focus on teaching learning methods, not just imparting knowledge. Of course, learning knowledge is the carrier of learning methods, and it is unthinkable to have only the latter without the former. Once a student really grasps the method, he can seek knowledge by himself, even if he "forgets" all the knowledge he has learned before.
3. School education is to provide an opportunity to go to a higher platform, and to become a real talent is to get out of school.
Most of the knowledge taught in school education can be forgotten after the exam.