@Mame,
I did a Google search and some of the national teaching associations, in their statement of ethics, allude to the fact that anything in your past that could affect your effectiveness as a teacher must be disclosed. Depending on how you want to interpret that, appearing in 3 commercial porn films, in-between teaching jobs, might fall into that category. They also refer to engaging in any sort of behavior which is detrimental to the professional image of teaching, and appearing in porn might come under that.
So, it's also about the ethical and professional conduct expected of teachers and not just about the laws regarding disclosure.
If it's something you don't disclose because you know you might not be hired if it was known, you could be accused of being deliberately deceptive by this act of omission. A subsitute teacher in Florida was fired this year after his past history of appearances in commercial gay porn became known.
One thing surprised me in my reading on this issue and that was that teachers do not have fully protected rights of privacy, particularly non-tenured teachers. Teachers have been fired for sexual adultery, for instance, and the courts have sided with the school districts, and not the teachers, in such cases. So, in practice, the courts seem to allow communities considerable leeway in the types of "moral" behavior they can expect and require from teachers.
On the other topic, of the FAA chief resigning after his DUI arrest, that man was a top administrator at the main federal agency dealing with transportation, the main agency in the country most concerned about drunk driving on our roads. So, he could not have survived at his particular position, which was under the Department of Transportation, once he was charged with DUI--his transgression/crime was clearly at odds with the precepts of his own agency. And, at that level of government, when they place you on leave, which they did with him immediately after his arrest, they really expect that you will hand in your resignation to avoid further embarrassing and tarnishing the current administration. That man had to fall on his sword and resign ASAP, which he did.
Other public officials could be arrested for DUI and it wouldn't require them to resign, because the nature of the crime wouldn't be so closely tied to the nature of their jobs. This man's job was involved with transportation safety, so for him to violate transportation safety, by driving drunk, on the wrong side of the road, meant he had to go, and he understood that.
It's unfortunate all around, because he was needed in his position, and they really can't replace him until after the presidential election, because the administration doesn't want to get embroiled in a confirmation process now, so the deputy chief of the FAA will fill in until then.
They kept their frenzy going for over a month and the opposition party took it up and ragged at the govt every day in the Legislature so it was a surety she'd have to go. I believe she was appointed without an inquiry into her driving record. 