Relationship in access table wont cascade delete

In my form I can add classes and if i delete a student it cascade deletes successfully so I know my relationship between class sessions and the link table is ok, I can delete single or multiple students or the class session in entirety.
I have a balance table, every time I add a student to a class it updates that and takes away a credit.

I wanted to be able to cascade delete the balance record for that session if the student was absent or the session got cancelled.

So I put the balance ID into the link table too, that allowed me to create the relationship but when I delete the class session the cascade delete works as mentioned before ie the link table entries get deleted but not the balance entries in the balance table itself.

I must have the relationship wrong but I am not sure how to achieve this, the balance table does have the student FK in it too.

Ive added a picture of the relationships and also the class form too.