What is the last step an educator can take to convince a parent to allow their child to read a particular book?

I believe that if a students parents were being so conservative about what their child is reading that the students education would be imp0acted by their parents choice, I would take it as far as possible. I understand when parents have controversy with material and will definitely be willing to find alternate reading but in the article I read the parents weren't allowing their students to read anything that wasn't in a wonderful world with perfect people and happiness. This to me does not represent the true cannon of life and in my opinion would greatly hinder someones ability to mature as a productive member of society. If I was in this situation I would do everything I could to convince the parent otherwise, then I would go to the principal, and if still necessary take it as far as the school board. Parents have the right to say what their kids can read but the student also has the right to a proper, valuable education.