I don't think teachers give a thought about the role of fathers in their students' lives. I think they're just so used to the modern family model where the husband is too busy with work to really get involved. And I also suspect that, that to them, D doesn't change their observation of parental involvement.
I suppose a widower would be a different story because the mother is simply not going to be present. But that's not the case here (although I feel like I've been widowed sometimes.)
I suppose I will just have to win them over by participating all the more harder, to prove their misconceptions wrong through actions and words.