I recently received a refund check from my school but I pay for my tuition out of pocket, is this a mistake? I don't understand where this money is coming from.

I pay for my school myself and do not use any loans, grants, or scholarships. I recently recieved an email from said school stating that I will be recieving a refund. I don't understand where this refund money is coming from. I'm wondering if this is an error on their part or if I'm just naive to this.