Nice idea for conflict. Schizophrenia gives you a great internal conflict. What's awesome about it is that it threads the gap between man vs. self and man vs. man. Except the other man is really himself. So cool.
I definitely can't write your introduction for you. Your teacher is going to be able to "hear" the voice within your writing, and he/she can usually tell when something isn't from you. Plus there is the plagiarism issue.
My first recommendation for your story is to write it in first person. That allows you, the writer, to really show your reader the internal mental conflict. You could have your protagonist having conversations with himself within his own mind. Perhaps you could have your character be struggling with developing relationships with people because his schizophrenia is constantly sabotaging his "reads" on people.
Regarding the specific introduction, have it narrate a bit of background. Something like "I wasn't always like this. The voices weren't always there. Well perhaps they were always there, but before I could always ignore them. Now though, I can barely figure out which voice is really me. They can't all be me. Can they?" That kind of introduction forces questions into your reader's mind. Readers that have questions are readers that are hooked. Hooked readers keep reading.