Yeah, this still is really interesting, who gives the kid their shirt? I guess their immediate family, but then again, how long can a shirt last? Now that person needs a new shirt. Piecing together rags makes sense, still, you need to have a collection of rags and some way to stitch pieces together, all of these are resources that seem like they readily available, but that's because I don't know what was readily available :)

Kids don't stay the same size for long, and clothing, shoes, and so on can be mended. You also had a larger pool of local resources to draw on than just the immediate family. (Nothing was thrown away until it couldn't be used for anything else.) The concept of hand-me-downs (and darned socks, for that matter) was ordinary when I was a young child, and while I may not be young by many people's standards, I don't quite go back to the late medieval. Depending on the article of clothing, going through three or four kids would be pretty normal. (Knee patches were pretty common on "play clothes", and there was a difference between your school clothes and your play clothes. If dungarees were involved, you actually wanted to be the second or third in line so you could bend your knees without much effort.) By the time I was entering my teens, those habits were pretty much restricted to infant clothing.