Your second journal entry is totally incorrect. It's simply
Accounts Receivable 3,500
from the tuition fee recipient's point of view. From the student's point of view, the first payment is:
Tuition Fee 8,000
Accounts Payable 5,000
and the second payment is:
Accounts Payable 3,500
Note by paying the second payment, the student is essentially converting the tuition fee recipient's Accounts Receivable into Cash. From the student's point of view, the student is converting cash into reduced Accounts Payable.
Edit: oh, and if your accounting program supports it, you might want to add this line to the journal entries:
Tuition Fee 0,00
The idea is that it helps you remember to which account the Accounts Payable / Accounts Receivable transaction is related to. The Tuition Fee account is not part of the transaction otherwise.
Or, you could have hierarchical accounts
Accounts Receivable / Tuition Fee (for tuition fee recipient) and
Accounts Payable / Tuition Fee (for student).