Regardless if your school allows an attorney to appear at a disciplinary hearing or not for an academic misconduct case, you absolutely should have somebody in your corner from the start of the process. You cannot expect the school to respect your rights or even respect the fact that you should be presumed innocent until proven otherwise.
At many public schools, colleges, and universities, that is, attorneys are allowed to be directly involved in the process from the start to the conclusion, including disciplinary hearings themselves. The role that an attorney would serve in such an instance is as the student's advisor. At many private schools, colleges, and universities, an attorney is not necessarily allowed to be directly involved in the given case, but there's no preclusion from an attorney helping a student and his or her family in a behind-the-scenes capacity. Because so much is at stake in an academic misconduct case, and because you cannot depend on the school to do the right thing or to respect your rights and interests through the process, you absolutely should have an experienced ally in your corner. An experienced attorney advisor can help and should be involved from the start, regardless of if your school allows the attorney's direct participation in a hearing or not.