Creative Writing help?

Hello everyone ,I have creative writing and my ignment was to write a short story of the topic my teacher choose .Which was my senior year or senior year; Im so confused i do not know how to write this. Im no where near being a senior im a sopre, I dont need this to be written for me im not lazy, im not wanting or asking you to d homework .tThat's my job i just need some brainstorm ideas to get started. Thanks :)