Genre: Short Story/Mystery/Thriller
I find the cover to be interesting and the title to fit your story very well. However, I do feel that the font of the title makes the cover look slightly messy. Perhaps something more clear that stands out would make the cover very attention-grasping.
"Great now were stuck arranging books..." Here, the word "were" should be changed to "we're" as in "we are."
Something that I noticed throughout your story is that the tense changed. Be sure to pick one tense to write your story from and maintain it throughout the book. For example, in the first paragraph, you wrote "he said teasingly" then later wrote "...as they think of what should be..." The word "said" is in past-tense, and the word "think" is in present-tense. I saw little mistakes like this occurring very often.
In addition, you sometimes confused plural words with singular. When multiple people are participating in an action, speaking, etc. plural words should always be used (they, them, their, etc.). When only one person is speaking or participating in an action, the words used should be singular (he/her, his/hers, him/her, etc.).
I also noticed that you go back and forth between characters instead of picking one single character to follow through the story. In the first chapter, you wrote "Their heart beat fast as they think of what should be the best thing to do in the situation." Here, you are describing the direct thoughts of two characters. This can be extremely confusing to the audience, so it is best to pick one character to tell the story from and maintain that viewpoint as you write. In this area, you also used singular-form words to describe what multiple people were doing.
Another thing to keep in mind is that you do not need to capitalize entire words or use multiple punctuation marks to show emphasis. Instead, you could italicize a word and put an exclamation point if what a person is saying is exclamatory and needs to be emphasized. Otherwise, italics are not needed. For example, you wrote: "...who told you to be late on my class AGAIN?!" Additionally, some areas are missing commas and other necessary punctuation, which creates run-on sentences.
I find that your story as a whole lacks descriptions, which makes it difficult for your readers to imagine or connect to the story. I recommend you go back through the story and add little descriptions wherever possible. Be sure to use as many sensory details as you can: what the setting looks like, smells like, sounds like, feels like, and tastes like. Without these details, the audience can hardly visualize any part of the story. Additionally, you should incorporate more thoughts and feelings to your characters. You don't describe many of your characters' thoughts and ideas, which makes them seem very bland and lifeless. Add in little details about what they are thinking and how they are feeling. Are they ever scared? Nervous? Excited?
Even though your story is a short story, I still suggest you organize your writing into multiple chapters/sections. The story is short, but it is also fairly long for occupying one single section. Lots of readers also enjoy reading shorter sections, so you may consider splitting your story up in suspenseful places and creating multiple sections out of it. By doing this, you will be drawing your readers smoothly into the next sections.
Even though this is a short story, your characters could be much more thoroughly developed. They all seem very basic, and none of them have any particularly interesting traits that stand out. You primarily describe who the characters are through dialogue, but you don't show much about appearance or what the characters are thinking. Without knowing how the characters think and who they are, your audience feels no connection to them and cannot relate in any way.
Overall, I think the story could be improved. The plot is interesting, but I think there is a lot that could be built up on it. With some grammar corrections, extra sensory details, and more characterization, I think the story could go a long way!