Contrary to the reviewer before me who called this "almost hilariously bad", I would like to say that this is not a bad movie. But it doesn't follow a lot of movie conventions, which is where I think a lot of people will dislike this. It is a very interesting movie and I would cautiously
say a good movie, but I would not recommend it for the majority. This movie is only for you if you enjoy arthouse films whose purpose is not the plot but commentary on social dis-inhibition and human behavior.
The entire movie works on exploring the situation at hand. Where awful things happen, people are shades of grey, and when the authorities do take charge it doesn't necessarily make things better. The depiction of what happens in housing estates and low-economic areas is realistic, but exaggerated. It shows how kids who grow up in these areas, who are living on the unemployment line, who don't want to have a job because their options are so limited and shitty, strike out with violence and posturing in gangs, depending on drugs while they spend most of their time idle. They stop caring about the consequences of what they do and find refuge in other kids who similarly want to rebel. It shows the vicious cycle of how kids coming from the background of relatives who are criminals learn from them, going out to commit crimes themselves, laid on a background of abuse and neglect. It shows how the police lose in the battle to keep control, and how excessive force doesn't necessarily achieve anything except reinforcing violence. Despite the ending of the film, where the streets are peaceful, you are reminded that this comes at a cost, and that those kids taken to jail in the riot will be back on the streets eventually, but now will be hardened criminals after their time in jail, just like their relatives.
The purpose of the subtle characterization is to show how everyone is flawed, just trying to do what they think is right, none of them finding a solution that works. If the film has any one point it is that the system itself doesn't work, and people's lives are ruined because of it. Unemployment and poor social services breed angry kids who lash out, poor police methods are either not effective enough or incite rebellion, and the silent majority are left as witnesses who just try to get on with their lives when the smoke clears.