This blog post by a teacher in the USA provides a good idea on how to engage students in thinking about online ethics.  It involves working with the students to come up with their own online ethics statements for their classroom, voting on their favourites, and collating the top-voted statements into a contract to which they then sign up to.

https://technologypursuit.edublogs.org/2015/08/19/creating-a-class-code-of-ethics/