Eugene,
Your question is very broad. The combination of the business logic for the student management system plus database normalization best practices will result in the right database schema for this platform.
Example business logic :
- User must have a B or higher to be eligible to move to the next grade or auto upgraded to the next grade
- User can be upgraded to the next grade but will not be eligible to enroll if the account balance for the prior year is not zero
Some of the business rules will guide your database design/model creation.
You need to be able to do the above resulting in an ERD which you can then share and someone can then offer additional feedback.