"Unexpected Transformation: A Year in the Wrong Uniform"

Question: Write a story about a teenage giy who was heading to a boarding school to finish high school. He had woken up that day to find that his sister had hidden all of his underwear, but he ruined her joke by just wearing the panties and bra that she had left him, even if the bra did make his chest look like a girls. After getting off the bus at the school he would live at for the next year, he was excited as he was welcomed inside. He was ushered through to the uniform shop, where he was measured and he was given a stack of clothes. He thought it a little odd that they spent a little while measuring his chest, but when he was getting changed he realised why. Because he was wearing his sister's underwear, they thought that he was a girl, and had given him the girls uniform. He had no choice but to put on the blouse and skirt, then the stockings and dainty shoes. Looking in the mirror he saw a school girl looking back. Due to his long hair, and even his name, he knew he made a convincing girl. It looked like he would spend the next few years at this school living as a girl, which could be fun.