That's to much in a short period of time. That's dangerous. Better for u to have that goal for next September_ the start of the new school year. That would give u 8 months to work at it. N u would look health skinny and not the sick skinny you get when fat is lost to quickly.
I was 210 and I lost 40 pounds in 6 months. I'm giving myself another 3 months to work on losing another 20 pounds
You're trying to lose 65 lbs in a very short period of time. You'd have to lose 16 lbs/month, which is almost twice as much as the recommended safe weight loss.
At 17 your body isn't fully developed and losing that much weight, that quickly, could cause you a lot of problems later on, plus it will be impossible to maintain the loss, as you'd have to use measures not intended for long term use.
Maybe you could look at a different dress or get it in a different size? It's good that you want to lose weight, but you have to do it with reason.