I dont know how it is where u work. But where i work i can start driver's helper right when i get off my 1st ups job. Driver helper's dont have a set time they are on call. You can tell your coordinator to tell your driver's since u wont always have the same driver when you are available. I believe that this would be perfect for you seeing as you are on call. You need to make sure though that drivers know you are unable to work at these times because if they call and u are unable to come over and over and over and they cant depend on you guess what? there not going to call. I believe this would be perfect for you they start loading trucks normally after the preload shift where i work which is around 9am so you could work til 1 or just go in after school. If there is no trucks running that late after you get off school then i would look for another job concerning ups seeing as there are many. Preload would be perfect for you, then u could go to school and after school have the rest of the day to yourself. But not sure now that i think about it if drivers helper would be so perfect since you are on call. Also this year where i work they are expecting driver helpers to meet drivers somewhere on the route i do not think this is right but apparently they do.