This question can unfortunately not be answered with a clear ‘yes’ or ‘no’. According to current trends, one probably has to assume that it was published for the first time as the student makes her homework available to a larger group of people. Everybody should know by now that Facebook users have virtually no control over the sharing of their posts. Even if the student only makes her homework available to a private circle (e.g. a selected group of Facebook friends), there is no guarantee that the Facebook friends in question will not share the homework with other people who are not known to the student.