Until the Industrial Revolution came along and turned children into cheap labor, children were the opposite: valuable labor. Either they helped out on the farm... or they helped their masters, and in turn their masters taught them a skill by which they could eventually make a living... Adults and children worked together, and there wasn't such a huge gulf between them. Not that children were considered mini-adults, unloved and exploited. Just that children were expected to rise to the adulthood all around them, not stew in adorable incompetence. (emphasis mine)