I don't think he owes UPS anything. The schooling assistance is used to cover the subpar wages we pay our part time workforce. Granted the benefits help, but since he's in school those really don't mean much for him either. Everyone works at UPS of their own accord, we don't owe this company anything other than the time for services rendered, work performed, etc and as far as I'm concerned they don't owe me anything other than my paycheck. I am grateful for the other benefits I get from working here, but never do I feel that I owe them or that they owe me. I understand UPS paid for his school but don't think we aren't getting "ours" from him. As my manager said "we're going to subject you to hard work and get the most out of you wherever and whenever we can (in the operation), in turn I suggest you do the same (employee discounts + earn and learn, etc) with us.
However to the original poster, I believe you will have to finish the semester (working at UPS), I don't remember the EXACT details as I've been on it for a couple years now (earn and learn) so now I just sign where it says they will pay for my school lol. Your HR department should be able to assist you in this matter as they seemingly handled all the questions and minor issues I had.