If you can't get a lawyer, it's not the end of the world, since you aren't being charged. The next step is to go in person to the office of the superintendent of your school district and deliver a very politely written, yet firm, letter formally requesting these documents. Or send it via certified mail, which might even be better.
Your point is to present yourself in the best possible light while telling them that they are NOT going to interfere with your education by suspending you for something of which you have no physical evidence.
Good luck- your family's tax dollars pay for your education, and if they are going to deny you that, they had BETTER have more than hearsay to go on.