Grades are a problem. On the most general level, they're an explicit acknowledgment that what you're doing is insufficiently interesting or rewarding for you to do it on your own. Nobody ever gave you a grade for learning how to play, how to ride a bicycle, or how to kiss. One of the best ways to destroy love for any of these activities would be through the use of grades, and the coercion and judgment they represent. Grades are a cudgel to bludgeon the unwilling into doing what they don't want to do, an important instrument in inculcating children into a lifelong subservience to whatever authority happens to be thrust over them.
I've been making a list of the things they don't teach you at school. They don't teach you how to love somebody. They don't teach you how to be famous. They don't teach you how to be rich or how to be poor. They don't teach you how to walk away from someone you don't love any longer. They don't teach you how to know what's going on in someone else's mind. They don't teach you what to say to someone who's dying. They don't teach you anything worth knowing.