I would talk to the teacher... Ask him if you can do like a 12 page paper. He might understand. He is an English teacher and they should be writers themselves. It's understandable.
If I was you, I would just keep writing until the end of the story. Then, you might be able to decide what's important.
I would take out little details, too. Or if they're going from one place to another, don't let them stop here, here, and here, just take them straight to their destination. Or don't let them stay too long in one place to interact with a ton of people. Does any of that make sense? Lol.