Percy could meet the school bullies. And they might pick on him at first, but then be in for a big surprise when he shows his strength. Also, he might encounter some teachers who suspect there's something different about him. Maybe a science teacher who notices his quick reflexes during an experiment or a history teacher who is amazed by his knowledge of ancient mythology.
In the fanfiction, when Annabeth goes to Percy's high school, she would probably form a study group. With her knowledge, she'd help Percy and his friends get better grades. Also, she might start some kind of architecture or history club in the school since she has a passion for those things.
Maybe Percy would struggle to fit in at first. He's used to a different world, like Camp Half - Blood. But with Annabeth by his side, he could start to adapt. He might make new friends or get into some trouble with the school bullies, only to show off his demigod skills in the end.
They could be involved in a high school project that turns out to be related to an ancient prophecy. Percy might use his water - controlling abilities in a science experiment in a really cool and unexpected way, and Annabeth would be there to explain the historical context behind it all.
He might meet normal high school students. There could be the typical jocks, nerds, and popular kids. Maybe he'd encounter a really smart student who is intrigued by Percy's different way of thinking. Or he could meet some mean students who pick on him at first but then learn to respect him.
There could be a school janitor who is actually an old demigod who retired from the hero business. He could give Percy some valuable advice based on his own experiences. And of course, Percy will surely meet Annabeth's classmates, some of whom could be friendly and some not so much, depending on how they react to the new boy in school.
One idea could be that Percy and Annabeth are new students at a high school filled with mythological secrets. They have to hide their demigod status while also dealing with normal high school problems like exams and bullies. Maybe they join the school's swim team and debate club respectively, which could lead to some interesting interactions.
One possibility is that Percy clashes with the school's jocks or popular kids. Since he's an outsider, they might pick on him at first. But then Percy shows them what he's made of, not with brute strength necessarily but with his quick thinking and his ability to outwit them. He could also get involved in a school competition, using his unique skills to help his team win.
It's possible that Annabeth surprises Percy at high school by setting up a whole new section in the school library dedicated to Greek mythology. Percy loves Greek mythology, and when he discovers it, he's thrilled. Annabeth reveals that she worked with the school librarian for weeks to make it happen. This not only surprises Percy but also enriches the knowledge of the whole school about their demigod heritage.