"As a result, using something like this could get a teacher fired."

This is not a concern in modern private schools. In addition to the Saas apps they use that display grades, homework (e.g. which book or worksheet and which problems), etc. they have blogs incorporated in them. In addition, teachers frequently send emails. Texting would be just another form of electronic distribution. There is not reason to focus on it specifically as a way that a teacher could get fired. They now have a myriad of ways to say something stupid, but that is the way things are.