In configure | setup data, make sure that you have your customer types defined, paying special attention to the default customer type.
When setting up the fees, set them up for each level that should have a specific fee.
NOTE: the default customer type fee is mandatory and must be the default fee. other customer / user type fees may follow in the section below the default fee(s).
When you review a student record, note the customer type associated with the student record. You can change the customer type on admin at any point, and your customer can select his/her customer type on your public ASAP portal when he/she firsts creates the student account if you have the preference for Allow Students to select their own member type during registration set to YES and have registration forms configured with customer types.