There is no case for treating young offenders differently. The emphasis has to be on responsibility. You have to concentrate on locking people up in the most human and civilized way. Young criminals are cultural criminals, a lot smarter than the treaters. You cannot deal with social injustice through the criminal justice system. If you try to correct in this way, you corrupt the system.
UK statistics show all previous forms of juvenile incarceration have failed. Of juveniles sentenced to community punishments (without incarceration), about half will re-offend; the figure for those released from custody is at least 82%. Approved schools were discontinued 20 years ago because their alumni reconviction rate was 49% higher than juveniles treated in other ways. The point is that child criminals are still children. There is a wealth of research to show that even "really persistent" juvenile offenders mostly grow out of crime; treat them wrongly, and you may criminalise them for life, leading the regular car thief to burglary, armed robbery or worse.