I was thinking about entering this in a local writing contest. It’s supposed to be for kids 9 and up. Can you please tell me if my sentence structure is flowing or if I have too many grammar mistakes? Anything is much appreciated! I know it’s long but bear with me!

Snowflakes fell from the dark clouds and onto the icy grounds. I sighed and looked up at the house. It was quite large compared to the ones back home and it had prickly bushes standing in a row. The snow covered its rooftops and chimneys. I bit my lip nervously and remembered Headmaster’s words: This is only temporary Clover, but you can make it forever as well. Your job is to watch over Chris, a 7-year-old boy and if you can do that successfully, you will be able to return back to Elmirr. Understand?
I was quite flustered at his words at that time. All I had done was turn Mistress Potts into a toad and now here I am, in the wretched human world; cursed to take care of a little mortal. Oh well, I might as well get this over with. How hard can watching over a child be?
With a wave of my wand, I immediately vanished and reappeared into a dark, lightless room. I looked about myself; realizing how neat and tidy everything was. Then, I used my eyes to scan and search for the boy. On top of a small bed and under the covers, I heard soft, tiny snores. I quietly tip-toed my way there; trying my best to not make a single noise. I stopped and dared not to breathe. I didn’t want to wake him up because humans thought of us as evil witches living only in fairytales and it’s best to have things remain that way.
I uncovered the blankets that shielded his tiny face. He was an average boy; with blond ruffled hair and a pale face and I continued to study him quietly. Though within a second, his eyes began to flutter and I panicked. I tried hiding below his bed but I realized it was too obvious. Quietly, I sprinted around, trying to find a better place.
“Ah!” cried the boy, “It’s a monster!” I turned around, my eyes looking wild and wide. The boy had his glasses on and his pointing finger towards me. I quickly turned myself invisible and watched his parents come running in.
“What is it Chris?” his mother asked with a worried look. The boy really did look as if he’d since a monster but that monster was not me. I’m a witch and there’s a difference.
“I-I saw a m-monster,” he stammered, “It was right there!” His parents glanced at each other, both obviously not believing the boy’s words.
“Maybe you saw a nightmare darling so it wasn’t real,” his mother reassured.
“But it was real mom! It was!” he exclaimed.
“Ah well, we can check in the morning can’t we? Besides, it’s getting late so go back to sleep.” She pecked his forehead with a light kiss and left; closing the door behind her. Oh but the boy was stubborn and so he sat there in the darkness as if he was just waiting to be eaten alive. I rolled my eyes and finally decided to reappear in front of him. He looked up at me; immediately ready to start screaming…again.
“Oh don’t start screaming now,” I snapped. He bent back, clearly taken by surprise. I sighed. “Listen,” I said, “I’m not going to bite. I just need you to give me a chance to explain a few things okay?” The boy hesitated with nervousness and looked into my eyes, finally deciding to accept. “First, let me make one thing clear to you. I am not a monster; I’m a witch and there’s a difference.”
“You’re a witch? That means you’re evil!” he cried with a gasp.
“No, I’m not evil!” I snapped, “Not all witches are evil.” The boy grimaced. Oh what a stubborn kid!
“What’s your name then?” he pouted.
“Clover,” I answered, “and I suppose you’re Chris?” The little boy nodded his head in agreement. I sighed. “Well Chris, I’m here to help you with your everyday life until I get to leave so…are you willing to work with me?” I held out my hand for him to shake. I’ve seen a lot of humans do that in their movies and stuff so I’m guessing this was appropriate.
Instead, Chris looked down and hesitated as if he still couldn’t decide on whether he could trust me or not. Then, he met my hand and smiled. “It’s a deal,” he said.
The next morning, I had decided to stay visible only in Chris’s eyes so that he knew I was still there. During the family’s breakfast of something called Cereal, Chris’s eyes would dart towards me every now and then. I didn’t mind though. After all, how many humans get to see us invincible beings?
Soon enough, Chris was ready to go to school with me standing by his side. While we waited for the bus, he looked up at me and asked, “Are you going to school with me too?”
“Sadly, I have nothing better to do so yes,” I replied with a scornful distaste in my voice.
He opened his mouth to speak but that was when the big, yellow old bus stood there with its doors opened. We both stepped inside and
It sounds familiar? Seriously? Wow! Oh and by the way, yes I already answered your question! Your story was excellent!
I’m 12 and I’m not thinking about publishing this but…who knows? Maybe if I have luck and worthy enough talent!
Please tell me what’s wrong with it and what I can improve!
Sorry about it being cut off. I hadn’t realized it. I suppose it was too long.

You’re 12? Wow, you write very well!
My only tip/criticism is:
Try to use ellipses as sparingly as possible. Even in dialogue. You may be using them to show a pause, but they slow down your writing and make it a little too informal or make it sound like the author has no idea what she’s talking about.

Other than that, it’s fabulous! Good luck in your contest!