Heya! May be this? http://www.mangago.zone/read-manga/july_found_by_chance/
Idk if this fits ur description but: http://www.mangago.zone/read-manga/miss_not_so_sidekick/
http://www.mangago.zone/read-manga/suddenly_became_a_princess_one_day/
http://www.mangago.zone/read-manga/the_reason_why_raeliana_ended_up_at_the_duke_s_mansion/
They sort of fit your description but I can’t recall whether they were school students in their past life.
Jkjsklaskasl ahh thank you!!!(づ￣ ³￣)づ
Hiya!! This is a long shot but hey ho. I started a korean manhwa a while back. It was about a highschool girl who was a background character of another manhwa and was aware she was stuck in this manhwa world. She was trying to change her destiny to make herself the main character. I started the manhwa and really liked it but unfortunately didnt catch the title before losing it. Please help thanks!!