There is a m-m relationship between the discounts and the students to which they apply. Your schema defines the discounts for the session but does not connect them to specific students. That needs a junction table. StudentFeesT looks like it might be the junction table for SessionFeeStructureT but there is no relationship defined.
StudentFeesDueT does not need StudentID or AcademicYear. It also seems to point to SessionFeeStructureT but with no relationship defined. StudentAdditionalDiscount MIGHT be the junction table for SessionDiscountT but there is no relationship defined and the FK name is wrong if that's what it is.
Making two tables, one for session and one for additional discounts is just plain wrong. There should be ONE table for discounts and it should have a type code so if the student gets both discounts, there would be two rows for the student in the junction table.
It is so much easier to verify a relationship diagram when you use discipline in how you name the fields. Your naming is inconsistent, both in the actual names and in the use of the underscore. Personally, I dislike using the underscore. I finding annoying to type and jarring to look at but if you use it, do it consistently. It will plague you and anyone who has to modify the app later forever.
I also can't identify a table that defines the standard fees for the Session.