"My work may be garbage but it's good garbage." Mickey Spillane
As more and more writers attempt to force the Middle Ages to conform to modern sensibilities in regards to children, I am more amazed at the facts that they choose to exclude than the ones they bother to include in efforts to prove their theses.
Boys as young as twelve were subject to the draft (calling up the levies) and girls as young as thirteen and fourteen were married off in arranged marriages. Since both things were a commonplace, it has to be assumed that children grew up faster in this environment.