Really depends on the child. The movie takes place in the depression and all major characters are adults.
If your child can handle the violence, this is a sophisticated movie with pretty clear messages that are:
* a family can lose everything material and still stick together.
* most adults are responsible, and even if they make occasional mistakes they try as hard as they possibly can.
* sometimes, people have really, really horrible luck.
* specific examples of people struggling and the real problems that they face with varying success.
* examples of conflict that arise due to circumstances.
The boxing scenes are rough, but they're boxing, not gratuitous dismemberment, huge over-glamorized bombs or anything my teen son would consider "gun porn." In fact I think for teens who glamorize violence, this is a good reality check movie. It's not actually about the boxing, it's about the family struggle.
I also think it's particularly good for kids who are terrified of what would happen if they became poor, or who have feelings that poor people are in some way fundamentally different than they are.
I strongly recommend seeing this with your relatively sophisticated teen(s) as a shared experience that, even if you don't talk about it right away, might provide a valuable reference point in the future.
Very strongly recommended for 15+. (I'm very squeamish, but it was fine.) Girls/women too.