I was referring to underage girls... the word “children” might have been a clue.
Please read the article, I did; and the article makes no mention of pre-pubscent girls voluntarily selling their bodies. The article asks "Why do young girls, from middle-class families, with an education chose to become sex workers?" (paraphrased).
The context of the story is that these girls are young (implied sexually developed) and are chosing to sell their bodies for fast cash and the chance of meeting 'glamous' people and living the 'Happy Hooker' lifestyle (as in "Pretty Woman") without having to work or study.