Stop calling the ups store and register an account online with UPS.com. It is usually much cheaper and you can print out your label at home (or school, as the case may be).
Or, you could put it in the mailbox with no postage, put your name in the ship to address section and the person you want to get it in the return address section. The PO will return to sender for insufficient postage. 
Had a friend in college who sent every letter home that way, saved him about 30 cents each time. Doesn't sound like much, but it made a difference on $.10 beer night at the club. 
