ah, i see. (: well okay, here goes.

i don't know if it was intended or not, but the first paragraph is in past tense, while the second two are in present tense. that's not really a big problem though, since it could be seen as intended.

the first paragraph is one huge run on sentence. I would end the sentence after 'tosses them haphazardly into his bag'. then i would end a second sentence after 'and slams his locker door shut'. so it would split into three sentences, so readers don't have to digest this huge one paragraph/sentence, you know? also, using 'haphazardly' is a bit too... big? like, the rest of the fic is written is a very casual way, but then you're suddenly stuck in a more formal word like that, and it throws readers off.

the last sentence of the second paragraph is also one big sentence, so i would cut that up a bit. also, you've already mentioned that key's locker in very neat and organized, so there's no need to say it again.

anddd, you spelled "somersaults" wrong. (:

that's just my two cents, feel free to ignore this if you wish lol. i think you have great potential!