I have a vast family of fundamentalist Christian "spare the rod" homeschoolers with large families whose toddlers sit still and quietly in church SEVERAL TIMES PER WEEK for long services (like 3 hours long at times). In a family of 7 kids (or more), there may be strong willed ones, easy ones, ones with learning disorders, boys, girls, etc, but THEY ALL DO IT. Why? Discipline. They are literally "trained" as per To Train Up A Child by Michael Pearl to sit still and quietly at tables, in carts, at church, whenever. It is the same parenting style used in Amish and Mennonite communities (and probably the Duggars) and that is why ALL of those young children are quiet and still in public. We live in central PA among lots of Amish and Mennonites and their kids are ALWAYS GOOD, standing quietly in line at Wal Mart while everyone else's kids are going nuts. I have never seen one misbehave.
Is it a matter of "proper" parenting? Not to those who do not believe in forcing kids to do this. Because that's what it takes. Force and discipline unless the child is born with a still and quiet personality (RARE!!). To many parents, "proper" parenting is letting kids follow their natural impulses and leaving them home if they "can't" be still and quiet in certain situations. Many people feel disciplinarian parenting is wrong and psychologically damaging to kids. I don't. I was raised that way. We HAD TO sit still and quietly in church, in grocery carts, at libraries, in waiting rooms, wherever or we were disciplined. We could run wild everywhere else and had a lot of freedom as well.
So. By today's standards of parenting in the USA since the 80s, most people think certain kids CAN'T behave in public. What that means is, it's extremely difficult to make them and takes a level of discipline many modern parents think is wrong to enforce. I did take my kids into those situations and I did enforce until they got used to it. Most of my friends very much disapproved that I would haul a defiant tantruming child to a restroom for a swat after a warning, but who cares. I'm a single mom of three with no family near and no nanny budget and they came on EVERY ERRAND with me. So I COULDN'T be guided by their impulses and plus I believe it's valuable for kids to gain early impulse control. Because of it we could go to concerts, plays, and events and lots of things people said their kids "couldn't possibly" do. It has served my kids well, they are all awesome little students and participants in anything we do at 8, 6 and 5.
I've got one easy daughter, one spirited boy, and one extremely difficult youngest daughter. I'm not as strict as my extended family, and my kids are not as well behaved because of it, but I did use discipline in toddler years-much more so with the two more difficult kids. And I looked like one of those lucky people with easy kids I'm sure to people who saw us out and about most of the time (we had our bad days though of course). But I wasn't. I was consistent at home and out with consequences for ignoring warnings to behave in certain places and times, restaurants, etc.
Is that proper parenting? Not to some. People find their own beliefs and comfort levels and that is what's right for them.