few suggestions

Prepare the hard evidence -
主编派专家鉴定，认为抄袭成立。
经调解，本人同意署名为共同作者
大家同意，书稿付印

Make appointments and present the fact to the school president (or VP), school board of director(s), school attorney, and next step - state dept of education (if you are in state U or U of state - state funded), and prepare to send all to media (such as 20/20, 60 seconds...).

You may find our own attorney. Probable, no attorney will take your case.