“Children should be seen, not heard.”
At the turn of the century only the wealthy, as ever, invested in their children. For many families, globally, children were an investment: another source of income once they were old enough to work.
Most of the time we forget that the 20th century was still in the grip of child labor. Up to, and through, the early 1930s children were still being employed in the factories of the United States and other 'first world' nations.
The changing attitude about children didn't come from the U.S., though, but from Sweden, from the psychologist and philosopher Jean Piaget. He watched and listened to children.
Children don't think like adults. Many would say this is obvious, but it didn't use to be. Often it still isn't. Consider child abuse: when a parent blows up at their kid, or in depths of frustration tries to get them to do it right, they, the parents, are victims of this basic lack of understanding. They want their child to process things rationally, or 'use common sense': skills which their child simply does not have.
Piaget's model for children came at a time when many models were being developed, but Piaget thought a child is, basically, like a scientist: curious, exploratory, meaning-making. Childhood play, he observed, is a creative act. Children's answers and questions have a logic of their own, a wonderful and weird logic, that teaches us much about the human condition.
Unlike most adults, he didn't spend all of his time trying to correct children's mistakes and answers: rather he simply noted them and made theories based on his research that would impact education and how adults see children. We are moving away from the rote all the time: a kindergarten now is not what it once was. The idea that children need time and space to themselves, that childhood was itself an important and distinct time of life: all credit to Jean Piaget.