Tutoring as a undergrad student
Tutoring is definitely a great way to gain more confidence and knowledge in a certain area as well as help you to decide if you enjoy the subject/teaching it and want to go to grad school. However, it sounds like you know the class really well as you received an A+ and it isn't worth dropping a lecture just to tutor. Grad schools do not put nearly as much weight on tutoring to warrant sacrificing other things that would benefit you.