Although the general rule, in taxes, is that you must be the one making the payment, to get the deduction, there is an exception for education. So, the loan is irrelevant for who can claim the credit. As long as the student qualifies as you dependent, you can claim the American Opportunity Tax Credit (AOTC) for his education, regardless of who's funds were used to pay the tuition.
But, if you co-signed the loan, the loan money is counted as support from you, for the dependent support test.
