The words in the brackets are telling the actors what to physically do, meaning it would be a stage direction.
It isn't dialogue because that is a conversation between two people.
It isn't dialect because that is how a person speaks. There is no speaking in the brackets.
It isn't narration because it isn't spoken allowed for the audience.
It isn't a description because that is too broad a term more often used for emotions.
Answer:
A memorable moment of success would be when I recived my first all A´s report card Freshman year.
Explanation:
I´ve never had honor role nor a passing GPA before then, and working hard to achieve what I never had was the best feeling!