I'm thinking about flaunting my grades to my classmates.
What do you hope to accomplish by showing them your marks?
I want them to know how smart I am.
It's fine to be proud of your good marks, but it's impolite to brag to your friends about them. You should be happy enough with yourself that you don't need attention from others to make you feel good.
I don't have to listen to what you say. I think it's better to show off my marks to everyone and brag about it.
When you brag about things like good grades, it makes you seem arrogant and insecure. If you're proud of your grades, maybe you could find a subtle way to discuss them, but don't brag about them otherwise your classmates will resent you.