You may have your settings set to private but that does not mean your likes, comments or shares remain that way once you take action on another person’s Facebook profile or shared content. Facebook has made it this way and you are not able to change it unless you specifically ask friends to change the setting located under the settings area when someone hovers over your profile picture within a newsfeed.
I sat in on a Facebook “class” today at our local library. I didn’t learn much, mostly because the lady made most of it up.
There is an abundance of misinformation about Facebook, but one would think that if you’re teaching a class, you might double check what you’re teaching.