It depends on what you mean by positivism. Legal positivism is the idea that the law, as made by legislative bodies, ought to guide the legal process. This means that there would be no (or less) discretion in sentencing for minors, to cite one example. So the juvenile court does not reflect legal positivism. Decisions are made by the letter of the law, as interpreted by the judge. But if you mean positvism in a more general sense, then it generally refers to the idea that there are scientific explanations for human behavior. A positivist approach, then, would look at the socioeconomic background of a juvenile defendant, as well as at the range of punishments that might help to rehabilitate them.