The partner classes should realize a classification of the 10 things the most important for the students and create one or more ebooks. First, we could know each other (each pupil could write an article or publish a video of presentation (etc.) and the classes could meet with skype).
Then each student could publish an article (or a video, etc.) on his passion or on the thing the most important for him in order to share it with the others. Then, each class would choose how many ebooks students want to publish. Each ebook will contain the classification of the 10 things most important for the students.