About three semesters ago, I had this one class on the afternoon with a bunch of my other classmates, I used to enter the morning and afternoon class so it was easier for me. When exams rolled around they made me do exams later because of the way I was assisting the class.
One girl asked me for help because she didn't understood anything, so I started using my free periods to help her but she never understood a word I said, when her exam came around I did it for her, I'd done it before, she passed, I didn't.
I even missed classes to help her, I stayed with her until later in the afternoon to help her and at the end she passed the class and I didn't.