What is the purpose of grades?

My parents are the complete opposite...
They evaluate my learning based on my grades. So basically, all they care about is grades.

Also, with the whole balancing out your life idea (academics, sports, social life, and spiritual life), my parents are not too fond of that idea either. It's either school or tennis. This is all my parents basically care about.

The thing is, my parents don't understand that learning is more important than what grade you get. They believe that getting into a good college is the ultimate goal based on the grades one gets. I mean don't get me wrong, everyone wants to get into a good college, but along the way to achieving it, the students should learn instead of worrying about grades nonstop.

So, feel free to try to convince my parents that grades aren't everything. I highly doubt that they will ever change their minds about grades.