I love your painting style The illustration is good but I think you need to keep trying to find the way to tell the story. All of us here already know the theme of this month contest, which is:
"Haven brought it to "Show and Tell"... even though she never got permission."
So I think we will understand what you are trying to say, but with a total stranger ( for example my mom, who is standing next to me right now) will wonder what is going on in this picture. @evilrobot gave you some great ideas, it shows how other characters think about this huge creature. May be the school should be a little bit bigger so it's easier for you to draw some students looking out the door and window. Or you can add some students walking to school, show how they react. And trees in the background is bended because the creature is stepping on them....All to help telling this thing Haven brought to school is very unusual.
I hope you find that helps Your illustration is getting better!