I have a 15 year old and have directly observed the "tuning out mom" phenomenon. For whatever reason, my own dad voice still seems to bear weight. It's not clear to mom or I why that is, but I think the general consensus is that I'm less likely to weigh in on smaller things (state of hair, shirt tucking, etc), so that it's generally more "serious" when I'm involved, regardless of whether it's actually something actually more or less serious. Style-wise, I'm much more to coax than to nag or demand. (i.e. Not demand "do this now" but ask "when will this be done" and ensure a definite time is given as an answer and hold them to it)