Avoiding helping your friend can be seen as disloyal.
Tim is doing very well in school, and several of his friends who aren't doing so well ask him for help.
Tim wants to make sure he has time to keep up his grades.
Tim agrees to let his friends tag along when he goes to the library and follow along with his study routine.
Tim keeps making up reasons for why he doesn't have time to meet his friends and help them study.
Tim's friends start to get better grades after they try emulating his study habits and offer to help him in other ways.
Tim's friends get fed up with asking him and make new friends who will help them.