For what it is, it's perfect. It's not pretentious or sentimental or trying to be something it isn't. It makes no claim to be a film for kids as far as I can see, it's just a film about kids, facing real life situations, and managing them well. The adult players are integral to the story and there's a nice balance between the kids playing with other kids, and interacting with their far from perfect parents.
It scores high because it deals with happiness, sadness, success and grief in a realistic way, not getting bogged down with sentimentality or ramming 'important lessons' down our throats. I don't see why kids around the same age as the stars couldn't watch this, but as I said it certainly doesn't set out to be a film for kids. It's by no means hard-hitting, more quaint than edgy.
These four girls are all little stars and I'm surprised to see none of them have appeared in another movie. What their character show is is although we don't live in a perfect world, we can make our world perfect. Well done all of you :)