Sakura Academy

You're in serious trouble
Your parents, since they don't have much money, had to pay for you to attend an academy specifically for women; their budget only allowed for that. So now you're studying at an all-girls academy, but the only way you won't be expelled is if you dress as a woman, so now you are a woman there... You are surrounded by temptations, and you will resist. Since you are quite thin, it's difficult to tell if you are a man or a woman, so your friends think you are a woman.