It's possible to add discounts to students using two methods.

You can add automatic percentage discounts or an automatic monetary value for a student on the Student Edit page. After a discount is added to the student profile, the discount will apply to each individual fee applied to the student.

Another method to add a discount is when the student's invoice/receipt is generated. At the bottom of the page, there is an option to add a discount. Add the amount and the click to add it.