One of my favorite memories in high school was debating with one of my favorite teachers (who also happened to be my dorm father) about communism and socialism. I was against, he was for. Despite our heated exchanges, I do not recall one incident of him losing his cool and yelling at me to "respect the President!" In fact, Ronald Reagan was our nation's president at the time. So, no. I never got a lecture about how I shouldn't say anything disparaging about the sitting President. Carter, on the other hand... well, that's a story for another day.
Today, Fox News did a story on a North Carolina student who dared to dis President Obama and got yelled at by his teacher, a Social Studies instructor, as I understand it. Apparently, Social Studies teachers much swear a blood oath of undying fealty to their President and perhaps offer up a child or two on the altar of their god. If you want to hear the longer, version, it's here: