It depends on the specific fanfiction. Different stories might have Percy going to various places, like a magical realm or a distant city.
If Percy and Annabeth were to go to highschool in fanfiction, it would be a whole new world for them. They are used to the dangerous and magical world of demigods. At highschool, Percy might get into trouble for his impulsive nature, but his loyalty to his friends would also make him popular. Annabeth would be the girl who always has her nose in a book, yet she'd also be the one everyone turns to for advice. Their relationship would also develop in new ways, perhaps facing challenges from normal high school romances or jealous classmates.
Well, perhaps Percy and Nico could be transferred to Hogwarts through some sort of magical accident. Maybe they'd have to deal with the different magical system there compared to their own world. They could make new friends among the Hogwarts students and get involved in the typical Hogwarts adventures like the Triwizard Tournament or dealing with a new dark threat.
If Percy and Annabeth go to Hogwarts in fanfiction, it could be a wild adventure. Percy would likely be shocked by the lack of demigod - specific threats at Hogwarts. He might try to use his powers in the wrong way, like using his water powers to clean the Great Hall. Annabeth would be busy exploring the library and trying to figure out how the magic in Hogwarts works compared to Greek magic. They could end up teaming with Harry Potter and his friends to face a new kind of threat that combines the worlds of Greek mythology and Hogwarts magic.
They might face new challenges like dealing with difficult professors. In college, the academic pressure could be a big deal for them. Percy might struggle with some theoretical subjects, while Annabeth could thrive. And they could also encounter new mythological creatures that are lurking around the college campus.
One possible reason could be a spell gone wrong. Maybe a magician or a god accidentally casts a spell that sends Percy back in time.
Well, one possible plot could be Percy and Nico having to deal with typical high school problems like bullies. Percy might use his water powers in a discreet way to stop them. Nico could be the mysterious loner at first but then make some real friends as he shows his cool powers. And they might also have to hide their demigod identities from the normal students.
It could become stronger as they support each other through college life. They'd study together, share notes, and encourage one another during exams.
Well, Percy could be involved in missions to protect Stark Industries from threats that are related to the mythological world. Some of the mythical creatures might be after Stark's technology for their own evil purposes. Percy would use his powers to fight off these creatures and keep the technology safe. Another type of mission could be to explore ancient ruins that are now in the middle of a conflict zone. Percy's knowledge of ancient languages and his ability to survive in dangerous situations would come in handy, all while Tony provides the technological backup like drones for surveillance.
In a fanfiction where they go to high school, Percy would likely be popular for his heroic deeds and good looks. He might join the swim team and break all the records. Thalia could be the cool girl who rides a motorcycle to school and gets into trouble for parking it in the wrong place. Nico would be the mysterious new kid. There could be a plot where they have to team up to stop a monster that is lurking in the school basement.
He could go to New York City. It has a lot of water sources like the Hudson River where he can use his powers. Also, there are many places to hide from monsters.