BF issue

I'm a 16 year old, junior in high school and my BF is 17, a senior in high school. I'm throwing a Halloween party and my BF has been talking to me about how much fun we are gonna have on Halloween for what seems like forever. Now suddenly he found out his grade is having a party, which I'm not allowed to go to, and he wants to go. Is it justified for me to be mad? Or am I just being a hormonal bitch. Lmk...