What do you think about the first part of my story?

it's sort of intriguing to me, something most of us can relate to, but as a writer I would suggest you to give more details, describe it. what about the atmosphere? the location? where was the school located? facial expression? With regard to the letter, I'd write it this way "Suddenly, in the middle of their conversation, a letter slid out of Jake's locker, floating in the air slowly in front of his eyes ( so that they both could notice it falling ) ..." as the letter is the turning point. keep writing!