As the founder of the French New Wave cinema movement, François Truffaut was less experimental than his fellow rebels. The visual style of "The 400 Blows" is fairly conventional, yet the content was considered revolutionary in 1959 because it tells the story of a 14-year-old misfit mostly from the points of view of a bunch of precocious children. Like "Breathless" and "8 1/2" "The 400 Blows" is not a plotty movie; it relies heavily on the charm of the lead, Jean-Pierre Léaud, a fierce-eyed child actor who later became an accomplished adult actor. It helps that Léaud was well directed by Truffaut, who was clever in giving his child actors plenty of on-camera chores to do, so when the kids went through those little tasks and reacted to the challenges of the tasks, Truffaut and his cameraman managed to catch their uncanny expressions on film.
"The 400 Blows" is about a school kid who constantly gets into trouble with the authority, and as we are taken into his home life, we realize that he is being raised by a pair of parents who have serious personal problems of their own. There are many long sequences without dialogs; for instance, when the kid finally gets turned in to the police by his impatient father, the actual events of him being booked, put in jail, and transported to another prison are shown with matter-of-fact realism without any of that "Scared Straight" melodrama.
In 1959, to make a movie about a juvenile delinquent, an average director would probably opt to shoot it in the comfort of a studio sound stage where rambunctious child actors could be more or less controlled, and the movie probably would have wall-to-wall dialogs digging into the moral and psychological backgrounds as to why the child had gone bad. Yet, Truffaut decided to do none of that, and we are thereby treated to a charming and believable story about a rebellious kid fighting for freedom the way he knows how.
Trivia: The title of the film comes from the French idiom "faire les quatre cents coups", meaning "to raise hell".