In today's Daily News, Dr. Laurence Steinberg, a Temple University psychology professor and expert in juvenile behavior, points out that statistics show youth violence has actually been declining since it peaked in the mid-1990s, despite a spate of recent attacks by juveniles on unsuspecting victims.

According to National Center for Juvenile Justice statistics, in 1995, almost double the number of juveniles were arrested for violent crimes than in 2009.

Specific statistics on juvenile violence in Philadelphia weren't available, but FBI violent crime statistics show that the city's violent crime rates have dropped in recent years. In 2000, there were about 1,503 violent crimes per 100,000 citizens, compared to roughly 1,238 violent crimes per 100,000 citizens in 2009.

"There's some question about whether [juvenile crime] has risen a little bit in recent years, but it's nowhere near what it had been," Steinberg says. "Everybody has theories about what makes crime go up and down and none of the theories is usually correct. The fact is that no one really knows."

Steinberg says that despite recent attacks perpetrated by juveniles, it's hard to tell whether there's been a true rise in youth violence.

"If we were living in a city where crime was very rare, then I think we would be much more curious about why two very similar crimes occurred within the same period of time," he says. "But in city like Philadelphia, where violent crime is common, it could just be a coincidence."