To obtain what you are looking for with your current structure, you could have an additional column where you could add the grades for all the courses that each student completed, separated by a comma.
I would, however, advise against this approach because it is a workaround and while it might seem beneficial as it keeps your tables number to 2, it is not a very scalable system and prevents you from being able to use data analysis fields like rollups, counts, etc.
I would instead suggest adding a new table called “Course Enrolments” which matches students and courses. Then for each of the records in this table you could have a grade field, a notes field and any other fields you may want to keep track of.
Hope this helps!
Calendly: Calendly - Alessio Monino