If the filmmakers wanted to explore the sexualization of children, why not make a documentary on the topic instead of...sexualizing children in your fictionalized story? It's not like these are older girls playing younger kids like they usually do, these are simply 11 year old kids. I dunno. I haven't seen the flick, doubt I'll watch it though.
I get the issue is using young girls to portray it, and it makes people uncomfortable, but that’s probably the point.
Dance troupes for younger girls often are guilty of such things, and the movie is perhaps asking what effect it has on them as a result while also holding a magnifying glass towards the society That does so.