In addition to teaching at a U.S. university, I also do some private tutoring on the side. I am always scrupulous about observing my university's conflict of interest policy, which prohibits tutoring a student who is taking a course that I am currently teaching (even if he is in a different section of the same course). When I'm wearing my "university hat", I know I am bound by FERPA, which prohibits me from (among other things) discussing any student's academic performance with his or her parents, regardless of whether or not they are paying the student's tuition. (Some parents have a hard time with the idea that they are not allowed to be kept informed of their student's grades.)
It's not clear to me, though, whether the same prohibition applies when I am wearing my "private tutor" hat. In particular, if a parent is paying for private tutoring for their college-aged child, and that parent wants updates on how those private lessons are going, am I allowed to divulge that information?