I'm an MFL secondary teacher with a child at the same school. For parents evening, I made appointments with DFD's teachers before I dealt with my pupils, then gave my pupils free choice of the appointment slots I had left in which I wasn't due to be on the other side of the desk. Had DFD's parents evening been at a different school on the same day, I would have gone to hers and given the parents of my own pupils the choice of an email or a phone call. I don't have a partner who can attend in my place.
At secondary level the child tends to come to parents evening along with the parents (at all the schools I've worked at, anyway). If I were to sacrifice DFD's actual parents evening to do parents evening at the school I work at (if DFD were at a different school, for argument's sake) all of her subject teachers would be spoken to over the phone by me, which wouldn't give her the chance to have a three way conversation with myself and her teacher about her progress for any of her subjects. If I were to go to DFD's parents evening with her and miss my pupils', they would get this in every subject but mine. I think that's the fairest way of doing it on both my daughter and my pupils.
Theapprentice I think it's very different at primary level. It's much harder to arrange to see 9 or 10 teachers on a different evening, plus you don't get the child-parent-teacher interaction as I mentioned before. The teacher also can't whip out your child's GCSE mock paper along with annotations and corrections over the phone, and talk both you and your child through it together.
Another point to make is that as both a teacher and a guardian, my priority is my one foster daughter, not the 29 in my class. Of course I want my pupils to do well and will do my utmost to help them do so, but ultimately my own child comes first. Yes teaching is my job, but ensuring my own DFD is making progress is also my job as her guardian. In more than 20 years of teaching I've never known a HT be unreasonable about a teacher missing parents evening for their own child's provided they offer the parents of their own pupils an alternative way of getting a progress report, such as a phone call or email.