I got into some trouble when I was younger (I was older than 13). I got in with a bad crowd, I did bad things. The changes in my life were unmistakable, but my parents never sat me down and tried to set me straight. I wish they had. I suspect that they didn't know how to do it, didn't want to damage our relationship, or something else.
I eventually got straightened out, but I lost a good 10 years, wasting my time doing things I shouldn't have been doing. I was quite lucky things didn't go worse for me. Two of my friends died -- and even their deaths did not help me see the light. My wife is the one who rescued me.
Adults should sit kids down and have a talk when it appears that the kid is going wrong. It doesn't have to be angry or confrontational. But to "look the other way" is to make a terrible mistake. At 13, I don't think the kid can fix this by himself. He's young enough to get into trouble, but not old enough to have tools to dig himself out. He needs help.
You lucked out, Buddy.