This questions pretty loaded, there are a ton of of ways you could do this, it depends on how you want to store your classes. I would think the most common solution would be with a junction table Many-to-Many

Make a ClassT with the classes (again lots of ways you could do this, keeping it simple (Math) or including years in the class name (Math 2024) or using another junction table to link simple to the different years, lots of options). The important thing to figure out is how do you want to handle next year, when this student is no longer in the class you would still want to have his old records so you can't just remove him from the class. (it goes even deeper after this with assignments and scores)

However you decide to do it though, it's just a simple relationship just like the student and parent. Then you display it the same way in a subform.

I agree with Adam. It's just another M2M relationship between student and class. Set up another junction table. You can then put a second subform on the Student form so you can see his classes.