I had the exact same thing happen when I was a kid; my kindergarten teacher swore up and down that I was completely illiterate, cause I'd take the baby books in the classroom, flip through them, then never touch any of them again. My parents kept informing her that no, seriously, the kid can read, the kid is reading full chapter books on their own, of course they don't give a shit about See Spot Run
Teacher continued to insist they were wrong and in denial about their kid being illiterate. She throws such a shit fit over the matter that the principal has to get involved, and I am brought to his office for a specific literacy test in front of him, my teacher, and a parent. they expected my mother to show up, on account of it being 2004. Mom has a full time job doing something sciency at the pulp mill, and no time for this nonsense. Dad runs a small construction company, and absolutely has time for this nonsense. We're off to a good start already.
Teacher is very smug about this, fully expecting me to once again prove my complete dumbassery. My daycare was attached to the school, and that's allowed me to build a reputation in advance. I'm that one kid that slammed their own head into a windowsill for unclear reasons, then failed to understand why adults were concerned about the blood pouring down my face. I've accidentally wounded myself so many times that my incident folder needed to be expanded. There is significant evidence for me being a dumbass of epic proportions.
Unfortunately for my teacher, I'm also a dumbass who can read.
I am handed a book. It is a picture book about an elephant. I refuse the book, because I find it boring and patronizing. I have no idea what we're all doing here, and nobody has made any real effort to explain the situation to me. The teacher looks triumphant. The principal winces.
Dad persuades me to just read the dumb book out loud. I begrudgingly comply.
I tear through the entire thing in about a minute, then throw it aside in disgust.
Dad was prepared for this moment. He is here to produce maximum chaos. The principal and teacher are still trying to understand what the fuck just happened, when Dad produces a different book and hands it me. He suggests I read a chapter of that to everyone.
I take the book, and happily begin reading Harry Potter and the Chamber of Secrets.
The principal is giving the teacher an unimpressed Look. The teacher is torn between wanting to strangle me, and wanting to strangle my dad. My dad is 6'3, which means neither option is very appealing. Neither staff member was emotionally prepared for a five year old to break out a novel. Dad has been arguing about this for weeks now. He is enjoying the vindication. He helpfully informs the principal that I've already finished the first two books, and am eagerly awaiting my older sibling being done with book three so I can start reading it.
The principal, now looking very tired, suggests that maybe I should go back to class now.
The teacher hates me with a passion and vengeance for the rest of the year. I am an autistic five year old, and therefor completely oblivious to it. I remain unaware of this entire story until my parents explain it to me as a teenager.