Listen to what Clowniac says. This clown-lover's storytelling skill is actually very very good. Check out his/her story and do note how the story is constructed.
Just to slightly expand on some of Clowniac's points:
Here's a brief IQ scale, according to the wilderdom website:
And I do agree with Clowniac's point: Just take out the number. By saying "she always blamed that on her ridiculously low IQ" the meaning isn't lost, and you avoid using numerical values. One reason is that it's like saying "His fist strike contained the force of 8,000 kg" vs "His fist could shatter a huge boulder". You can relate more easily to "shattering a huge boulder" than you can to "force of 8,000 kg". Same concept here: "Blaming her low IQ" vs "IQ of 65".
Though personally, IQ is a good indication of your rough understanding of "what's expected", but it doesn't determine your intelligence level. I don't put much faith in IQ scores, because people tend to blame it on the IQ. When someone says they can only do "so and so" or they're struggling to do "this and that" because of their IQ... well, it's now a scapegoat. It was originally there to help give an indication of intelligence, and it doesn't define them. But it's now an excuse. Let me use a more extreme example:
"Yeah, I gutted and killed all the dogs in my neighborhood because my dad used to kick me all the time, so I had to vent out my anger."
The first part about IQ is minor in comparison to what you do throughout the rest of chapter 1: you (as the author) are actively talking to the reader. We're here to read stories, not have you talk with us. If you want to talk, join discord and talk to your fellow webnovel mates there. By talking to me, I'm no longer immersed into your story, and instead, am engaged in a a conversation—albeit one-sidedly—with you.
Here are the sections I'm referring to:
Well, i guess you understood what i meant when i said that she really struggled in her life.
No, actually, I don't understand what you mean when you said she struggled in her life. Getting called ugly and bullied in middle school? What a coincidence! I've been through that before too! Loner who spent summers in the comfort of her home without friends? No way! Same here! But did I have to struggle in my life because of those things? Nope. I had a wonderful family who supported me, I had books I can escape to, I had siblings who torments and loves me. So can I understand her struggle? No. Can I understand that she really struggles in life? Nope. I can't. All that I've known is what you told me.
If I told you that I have an uncle who has a kidney failure and requires constant care and attention, would you understand his struggle? Would you understand the struggles of those around him? Not likely. But if I showed you the struggles: he spent hours everyday on a machine to help do dialysis, every step he takes is accompanied by a grunt of pain, every bite of food is vomited back out, can barely sleep for more than 10 minutes each time.... would you understand that better? At that point, do I even need to tell you "I guess you understood what I meant when I said that he really struggled with life after his kidney failed on him"? Likely, no. You'll likely understood that, hey, he has it rough.
In a typical first year highschool class you would probably see in an anime, a short girl was sitting in the back looking at everyone making friends and reuniting with their old friends.
I've seen Great Teacher Onizuka. Does that count? Wait, I think that may be middle school. Highschool? Maybe Bleach? Naruto (they do have a highschool equivalent)? Don't rely on my experiences.
" It's My first day in highschool! i shouldn't stress so much already! There will at least be one person approaching me to become friends." thought the short girl, who is Anna as you may have guessed.
Actually, I didn't guess. I wasn't even guessing at this point. All I am trying to do was to try to re-immerse myself back into the story, and you just pulled me back out.
Third point: Show, don't tell
Don't tell us what's going on.
Let me note one section that could use "showing" and not "telling".
The whole class was alarmed and looked at her like they were looking at a crazy lunatic but they soon turned away and ignored her and then resumed talking to their friends about the start of their highschool years.
How can you show me that the whole class is "alarmed"? Maybe a few people jumped up? Maybe everyone turned and looked at her? Etc.
There are various resources out there for you in regard to "showing":
Fourth Point: Suspense
There is a lack of anything suspenseful in your story. Suspense drives your story. It causes reader to turn it from one page to the next.
In your story, you introduce us a character that is... well, struggling with everyday life due to her low IQ. But that's literally all you did, introduced us (aka: you "told us") with one line about it. There's many ways to build suspense, Check out that guide to learn more about building suspense.
One way is to do it with your character. Make it clear early on what she wanted (it must really matter to her), why she wanted it so desperately, what's stopping her from achieving it, and what would result if she fails to get it.
For example: you can show us an opening scene where her low IQ actually interfered with her life, and that it's impacting her negatively. Like people beating her up because she's "retarded" and constantly steals things from her. People talking in front of her like she's too stupid to understand. Show us that she really really struggles, and that she really really wants it changed—maybe she practices every day all the conversations she might be expecting the night before. She's standing in front of a mirror, reciting, "Hi Mr. Rogers, how are you today?" <pause> "That's good to hear that you're doing well." <pause> "Oh, sorry, I would love to chat more, but I need to go to school now." Then maybe she would berate herself for forgetting to raise her hand to wave "hi" as she said "Hi Mr. Rogers", so she starts all over again. Remember, show, not tell. It could be something simple, like people constantly looking down on her. Teachers constantly patronizing her. Show that her school or outside environment was about her trying to survive. Anything.
Fifth point: ALL CAPS.
I DON'T KNOW ABOUT YOU, BUT READING SOMETHING LIKE THIS ANNOYS THE DAYLIGHT OUT OF ME. MAINLY BECAUSE ALL CAPS IS USUALLY USED FOR 'SHOUTING', THEREFORE YOUR CONSTANT USAGE OF THIS IS SLIGHTLY IRRITATING AND JUST SEEMS OBNOXIOUS.
Plus, all my prior experiences with people typing in all caps were with little immature kids who still smells of baby powder. By doing all-caps speeches like this, you remind me of my personal experiences with other all-cappers. And I'll tell you right now, that wasn't a pleasant experience, and you're automatically categorized in that section too for using that.
Yes, I understand that it's your system talking. But please, can you just not format it in a different style? Maybe italicize it? or just leave it enclosed in your brackets? (Which, by the way, was something that you failed to consistently do for your system's speech. You stopped enclosing it in your brackets
 after a certain point.)
The amount of action going on in this first chapter is... very lacking. Everything was you trying to unload as much background as possible to me, the reader: From Anna's IQ to her highest grade, her life, Adam's popularity, his score, the system's whole conversation. Like, why would I care about this background information about something and someone I don't even know or can relate to?
Among other things that we may have missed, feel free to look for "chapter 1 checklists when writing" on google, such as this one.