I too am new to this site just learning from others is helping me find peace. I can see where you are coming from as I have dealt with the same issue. It was alcohol at first, then huffing, pot, synthetic marajuana, pills ect. I didnt notice the signs at first. I actually tracked my daughter down by her GPS on her phone and busted up parties.
The law is what really put her in line because she was out of control. We dont have an alateen around my area. The courts ordered her to out patient treatment which she has now been thru twice. We also went to DBT therapy together and she sees a councelor once a week. A lot of it was the teens she hung out with and all I could do was just keep watching and busting up the fun or trouble they were in. I would find videos and show her what this stuff did. When we went out shopping I would keep reminding her in the long ride home how much I cared and what this was doing to her & others around her. She is now 18 and didnt graduate. She is realizing what mistakes she has made but still blames me for some of it. Its hard, Very hard. I am excited to find a place like this where I am able to talk about things and get advice. To know I am not alone. Keep your chin up, take one day at a time.