How can a preteen work at the circus?

This must mean young persons of under 13 years and is not legal in England. However when I was a child with the old tenting shows the townsfolk children would love to help build up the circus for a payment of free tickets! This was always encouraged and great fun was had for the children. I suspect that the current much larger and heavier and therefore more dangerous outfits will not encourage the practice any more - yet another sad loss for childhood experience.