My warning is simple and very clear: if you are employed by a school (or would like to be) do not post anything on Facebook which could be misinterpreted by your present or future employer.
The issue is not freedom of speech. The issue is electronic media. It is everlasting.
Facebook posts can be shared. They can turn up on Google searches. They can be used against you by people who don't like you. Even when you supposedly didn't give them permission to do so.
So against this sobering backdrop, let's explore what's involved with Facebook.
1. "But my privacy settings were ultra-strict."
That's understandable. You only want to share your information with your friends and family. But remember: once you post something on Facebook, it's out there. It's no longer private. If one of your 'friends' decides to forward that photo of you hoisting a glass of champagne on your 30th birthday, that simple act of 'sharing' could cost you your job. It has done that for several teachers according to news reports which I found.
It's not just photos which can get you in trouble. It's your comments about your work or your students. If you want to self-destruct, then by all means post something like "My parents are arrogant snobs". That fuse will take only a few hours to ignite the bomb.
2. There is a wall between teachers and students.
That wall exists for a great many reasons. It's part of the way the relationship between teacher and students is handled. Period. But that also applies to Facebook. You don't 'friend' students until they are 'ex-students'. Even then, keep things just as proper and professional as they were when that student was a member of your class.
Put another way: you do not flirt with students. Period. In school or out of school. On Facebook or off Facebook.
3. Facebook posts last and last and last.
One of my young friends had a Facebook site replete with hundreds of photos of him travelling the world in his undergrad days. Plenty of scenes showing new found friends sharing a glass of beer. But the minute he became serious about his doctorate and the career he planned once he obtained that degree, the Facebook pages came down. He hopes. The problem is that he's only safe as long as somebody didn't save some of those photos.
Google caches everything. Forever. If somebody knows what they are looking for, they will find it. Make sure what they find is squeaky clean. Ultra professional.
Bottomline: Do like we do at The Classical Station where I volunteer. We have a simple rule at the station: if we can't say it on the air, then we cannot say it in our conversations at the station. Simple. Clear.