IS: Otoko demo Onna demo Nai Sei (2003)

Haru Hoshino was registered as female at birth but raised as a boy. Haru enters a high school for culinary studies to earn a chef’s license, but must now attend as a female student due to the revelation of Haru’s birth registry. Haru has to deal with the confusion that results from her body’s adolescent transition to womanhood and her romantic attachments towards the male students.

Source: www.anisearch.com/manga/3068