One idea could be Merlin as the new student with mysterious powers. He tries to hide his magic from everyone, but it keeps getting him into trouble, like accidentally making things levitate in class. Another could be a high school version of the Arthur - Merlin relationship, where Arthur is the popular jock and Merlin is the nerdy outcast, but they become friends over time.
Maybe Merlin is part of a secret club in high school that is dedicated to protecting the school from dark magic threats. There could be a big event like a school dance where an evil sorcerer tries to cast a spell on everyone, and Merlin has to use his magic to stop it. Or, Merlin could be a talented artist who uses his magic to enhance his art, but it causes jealousy among other students.
A cool plot for 'avengers high school au fanfiction' might involve a mystery. Maybe there are strange happenings in the school like objects floating around mysteriously. Wanda Maximoff could be the one who initially notices and tries to figure it out with the help of Vision. Meanwhile, Black Widow could be the popular girl who is secretly a spy, investigating a possible threat to the school from the inside.
One idea could be that Ciel is the new student council president, trying to reform the school's old - fashioned rules while dealing with a rival group led by Alois. Sebastian could be his loyal butler and also a star student in various subjects, secretly helping Ciel with his plans.
One idea could be that the houses are like different cliques in high school. For example, Gryffindor could be the brave and popular kids who stand up to bullies. Slytherin might be the ambitious group that is always vying for the top positions in school clubs. Another plot could involve a high - school version of the Triwizard Tournament, but with normal high - school sports and academic challenges instead of magical ones. And a third idea is that there's a mystery about a hidden room in the school that only certain students can find, and it has secrets related to the founders of Hogwarts.
Well, a plot could involve Merlin being undercover as a new student who is actually there to protect the school from a dark magical force that only he can sense. He might have to form an unlikely alliance with the school outcast who turns out to have some latent magical ability. Or he could be in a situation where he has to participate in a school magic competition while hiding his true power level.
There could also be Mordred as a younger student who looks up to Merlin. He might be a bit of an outcast too because he has some strange abilities. Gwaine could be the class clown who befriends Merlin and is always getting into trouble. Percival could be the gentle giant, an athlete on Arthur's team who also befriends Merlin and protects him from bullies at school.
One idea could be a modern-day high school AU. Percy could be the new kid at school, a bit of a loner and a troublemaker. Annabeth, on the other hand, is the top student and part of the student council. They get paired up for a project and initially clash because of their different personalities. But as they work together, they discover they have more in common than they thought, like their love for the ocean (Percy's always been drawn to it, and Annabeth has a fascination with ancient sea civilizations).
One idea could be Naruto being the class clown who is secretly a really talented artist. Another could be a love triangle between Naruto, Sasuke and Sakura in high school, with Naruto trying to win Sakura's heart while Sasuke is the brooding, mysterious rival. Maybe there's a big school competition and Naruto has to lead his team to victory against all odds.
Well, perhaps in this AU, the female Naruto has a special bond with a different group of ninjas. For example, she might befriend some of the more reclusive clans early on. This could lead to new alliances and storylines. Also, her journey to become Hokage could involve different political and social aspects due to her gender, like having to fight harder against the traditionalists who don't believe a woman can lead.
One idea could be a sports competition at the high school where Naruto and his friends compete in a ninja - themed track and field event. Another could be a school dance where there are some unexpected alliances and rivalries revealed. Maybe a new student arrives who has a mysterious past related to the shinobi world.
One idea could be that the Avengers are all new students in high school. Iron Man could be the super - smart tech - geek who's always building cool gadgets in the school's science lab. Captain America might be the new transfer student who has a hard time adjusting to modern high school life but quickly becomes popular for his sense of justice. Thor could be the jock - like character who's a bit clueless about normal high school stuff but is really good at sports. And Black Widow could be the mysterious girl who everyone is a bit afraid of but is actually really kind.