My Platinum Lady

The super-expensive Joka Gakuen has a policy where the valedictorian, platinum student (PS), is exempt from school fees. Ai supports her large family in place of her parents, so she has little money. She takes Joka Gakuen's entrance exam because she wants to become the PS. Her dream comes true when she gets the top mark, but… Wikipedia The Doujinshi & Manga Lexicon Vol. 1 Vol. 2 Vol. 3