Her parents have no idea what is going on. They are a well adjusted, loving normal family. Her little sister finds out and keeps her secret. But keeping this type of secret is not easy. Before she decides to take off her shirt to play soccer she spends time eyeing her breasts in the bathroom mirror to make sure that she has no breasts because once she starts getting breasts, she going to have to make adjustments to keep up the deception.
She gets away with it until she gets into a fight and beats up a boy and then it all blows up. It seems that the outcome of the fight is more about the fact that a boy got beaten up by a girl rather than the fact two kids got in a fight. That's the issue -- that a girl beat up a boy.
Celine Sciamma tells a modern story about gender that is universal. The reason why it works is because it is so well written, so well directed and so well acted. The actress who plays Laure Zoe Heran is a revelation.
This is a movie that questions all the gender constructs of our culture and doesn't lay blame but really makes you think.