I'm a bit conflicted. And let me clear it that I'm not attached nor do I have kids.
On one hand, a restaurant is not really a place to be having a loud conversation, much less a phone call and a personal one. We give the same **** to people who act as such in airport lounges. Quiet conversation is one thing; being in a table greater than 4 patrons is another; and just being loud is yet another.
On the other hand, I'm not sure how it's framed, but it just may happen that that is the only time that parent has to talk to their child. Don't know how old the child is, or who is at home with the child. In a way I'm glad that this parent appears to take some interest in helping their child with school work, because many don't or don't care enough to even offer support for their children (i.e. reinforce positive learning behaviours if they don't know the content). At the very least, the conversation has to be the least ridiculous or offensive one in the range of public conversations that all of us here have criticised.
I'm also not entirely convinced with the label, "socially inept tosser".