Inappropriate use of Digital Media

Our High School is a 1 to 1 school which means each student has a computer of his or her own to use for their classes.  I have to talk to students frequently regarding the appropriate use of social media.  It is easy to make comments on Facebook or Twitter that can be considered offensive and students need to be taught that it is hard to tell if someone is teasing, being sarcastic, or playing around by reading a comment because you can't see facial expressions, or the tone of the voice, etc.