Anybody else got good grades by appearing confident?

I usually get good grades in school and so on, and honestly i dont study very hard nor am i super smart. I just tend to not worry at all and tend to speak/write like i know my stuff, and in all non-technical fields teachers judge that to be like i know my stuff. Its kinda unfair in my eyes, that i should get higher grades than some of the 6's or 2's or 1's who study super hard but get run over by nervousness or doubting if what they are doing is good enough. What i do isnt even conscious, its weird.