I wanted mine to behave in a socially acceptable way too. And they both knew what that was at that age.
The problem with this is that it is potentially more about your needs then your DC... Who determines this magical "social acceptability" anyway.
My parents were like this, very much of the authoritarian school that can undermine children's feelings and autonomy.
My father particularly would have agreed with the statement they will be in the photo and smile because I have told them too.
He hated any hint that his authority or control was being undermined and would get quite irrational with it, really realy irate [quite scary]
He had no interest in why his children felt the way they did, he was just determined to exert control.
And he had no desire to be shown up in front of other parents [particularly his siblings and parents, my GP] and that was his all encompassing need, to look like a parent in control rather than one who had emotional empathy with his DC.
I am 38 now and this still makes me sad. I think it may be part of the reason I live in a different country to my parents. And I definitely don't trust my parents with my emotional feelings [my mother was less strict but an enabler to my father and of the "stand by your man" school]
So all you posters who want "well behaved", "socially acceptable" children be careful what you wish for.
I also got myself into emotionally inappropriate relationships as a young adult [emotionally abusive] as I didn't give any credence to my own feelings of hurt and anger as I had been so well trained to.
Took a fantastic therapist and about 4 years of therapy to sort out [I was effectively "re-parented" as my therapist put it]