Cos at dd1's school it's strictly parents only. Now I can see that there are some advantages to this, that both sides can say things they might not want to say if the child was present.
But conversely, it would be quite helpful for the child to hear some things straight from the teacher's mouth, rather than relayed through the parent -- somehow has less impact that way.
I'd just be interested to see what other schools do -- I'm assuming the vast majority of secondary schools include the dc.