You were not specific about if the computer was provided by the school, if this was a personal computer that you bought to school or was your computer at home when the emails were pulled up by the "tech center"? Understand that when you post on social media, then this is going public for the whole world to see. Thus, you have no expectation of privacy and no legal protection.
Answered on Nov 22nd, 2016 at 6:39 PM