My name is Kellan Armstrong, a girl in disguise

“Hey sis. I just want to let you to know, that you’re good friends with the three people surrounding you. The one sitting in front of you is Stephen. You probably don’t recognize him, ‘cuz he’s been to the hairdresser. The person next to you is Cal. His real name is Calvin. Do NOT make him angry, or else I think he may be able to kill you. He’s your friend too! He can’t control his anger when he first gets angry, but I think you’re safe if you don’t speak much to him. The person in front of Cal is his childhood friend Alexander. He doesn’t speak much, so don’t get mad at him if he doesn’t answer. I think that’s all you have to know. Bye, bye! Don’t mess my life up!”

Heather is a 15 year old girl, with a twin brother. Her brother is going to Europe, but he doesn't have permission from the school, so Heather needs to take place as her brother in his school for a month. She finds out something she didn't know about her brother.
She experiences her second love, but what if the guy she like is gay?