You need to determine your priorities, which sound like school first and then
UPS, which at this point in your life is where they should be, and then relate those priorities to your supervisor. You are not the first college student to ever work at
UPS so they are well aware of your commitment to school and realize that you are here for a paycheck and the benefits but you must let them know. As far as the harder you work, the more work they give you, welcome to
UPS. I have been a driver for 19 years and my co-workers will tell you that I have yet to figure that out. Whatever--it makes the day go by that much quicker.