"Juvenile crime" covers such a huge potential concerns, and the time span you are addressing - sixty-two years! - is so long that it's going to be difficult for you to locate the information you are seeking in one place. You may need to narrow your focus to a particular area of juvenile crime; look specifically at teens involved in murders, thefts, assaults, or some other type of crime. You may also need to use a shorter period of time for your comparison.
Given those suggestions, however, the youthviolence link below has graphs representing various types of youth-related crime rates dating back to the early 1990's that could be presented via PowerPoint. The American-decades link from eNotes includes an article dealing with "Law and Justice" for each decade since 1900 in the United States. The articles don't have the hard data you want for a graphic presentation but do provide background information if you can use a commentary of crime trends through the years.