Ponyboy says 16 years on the streets can teach and show a person all the wrong things. What does he mean by this?

In Chapter 8, Ponyboy and Two-Bit visit Johnny in the hospital, whose condition has taken a turn for the worse. As Johnny is resting in the hospital bed, Ponyboy attempts to lift his spirits by telling him that everything will be okay. Johnny responds by telling Pony that he is scared stiff and is afraid to die. He then laments about the fact that he is only sixteen years old and there are still thousands of things he would like to do in life. Johnny proceeds to tell Pony that it isn't fair that he is about to die and hasn't seen or done the things he's wanted to do. Pony attempts to reassure Johnny that he isn't going to die and mentions,

"Sixteen years on the streets and you can learn a lot. But all the wrong things, not the things you want to learn. Sixteen years on the streets and you see a lot. But all the wrong sights, not the sights you want to see" (Hinton, 103).

Pony is essentially saying that kids witness most of society's ills when they are sixteen and living on the streets. Pony is aware that the kids in his town like Johnny witness violence, abuse, and a myriad of crimes at a young age. The kids living in the streets see and experience a lot of illegal and dangerous things, which has a negative impact on their psychology. Pony knows that Johnny has witnessed the negative aspects of society at a young age and feels bad that he will not get a chance to experience the positives of life.