I got divorced 4.5 years ago. My son was 17 at the time. He had become as good of a liar as his mother, which was quite a feat. He started smoking pot (as was popular) which led to the desire for something stronger. This also led to laziness in anything he didn't enjoy doing, school being one of those things. When he learned he missed enough school to not be able to graduate (he was 18 by then) he dropped out. It devastated me. He hadn't been talking to me for quite some time and his mother was the perfect enabler. I am a very straight laced person who chose to never touch drugs, and while I did some dumb things as a kid, I was a relative saint compared to pretty much everyone else while growing up. To choose to drop out of school not because of hardship or lack of opportunity, but rather because it was harshing his buzz, was, in my eyes, inconceivable.
He spent the next year partying and trying new and more powerful drugs. Each evening was a challenge to outdo the evening before. Get more high, get more wasted, party harder, get in crazier fights, and do stupider things. It culminated with him and 2 others breaking into a head shop and doing 12k in damage. They got caught on tape. Facing several felonies, the owner showed leniency and offered a deal: pay the damages and no charges. The other parents pressured me into joining as it was an all or none deal. My son, facing prison for at least a year, seemed to be "playing ball". He accepted my conditions: move to Idaho to live with my brother (get away from influences here), join the military, get his GED, and pay back the money. He got enrolled and had 4 months to kill before basic training.
First he got his GED, which despite not attending his senior year, he passed in one test with 95% and graduated with honors. The test, by the way, is designed so that 33% of high school graduates would fail. You have to know everything from grades 9-12 on the last tests, and it isn't that easy even though a GED is considered inferior to a high school diploma. This, of course, is in the U.S., but I can't imagine it is much different in CA.
He went to live with my brother, who has no kids and wasn't the best influence, but kept him out of trouble for the most part. He came back a couple weeks before deployment and ended up hurting his foot (old break that didn't heal) and had to have surgery with 12 weeks recovery, just before shipping out to Basic Training. The military changes his MOS from what he wanted to do (diesel tech) to something he hated the idea of (filing clerk), but he could still go. However, now back home, he moved in with his mom and soon was back into drugs. Then he got 2 Minor in Possession charges for alcohol (he was 20 by this time) and a pot possession charge. I stepped in again and got the charge deferred, which meant he could still go into the ARMY, as long as he finished his community service and counseling. He moved back in with me but lied about everything and in the end it all went to hell and I kicked him out.
He spiraled down the drain as drug use turned to dealing pot, and then meth. He wound up in jail on a distribution charge, and after a week I sent him a letter talking about our relationship and why I kicked him out of my house, etc. After 10 days in jail, facing another 6 months to a year before the trial (no money for bail), he reached out to me and I helped him again. He was put on a patch to monitor drugs and stayed clean for a year waiting trial. He got a job and I kept him on the straight path, although it wasn't easy and he almost slipped a few times. He is now on probation, been clean for about 15 months, and his hard work earned him a management position at the place he works. In fact, his hard work made enough of an impression on his bosses that they wrote letters to the court and in turn his sentence was reduced to just possession, no distribution. He is making damn good money and pays me rent, is paying me back for the bail and fines (totaling around $10,000 so far and he has paid off $8k of it already), is paying off all the stuff he neglected while on drugs (about $6k), and has a financial plan in place for the next year. He still has a few legal issues to finish serving before he is clear of it all, and after the probation which is another 15 months, he will have no felonies on his record. He has health insurance now and has been seeing a dentist to repair some of the damage from drug use. He is back to working out and trying to get his body back in fighting shape (he enjoys MMA fighting) but he also understands that fighting is a bad idea because it can mean injury, which could hurt his ability to do his job. He worked hard to get where he is (in an incredibly short time) and knows what it would cost him to lose it. Most of all, he is AWARE of what his past choices have done to his life, and sees how he can avoid that in the future.
The point of this story is to say that A) I have been there, and I feel your pain. Hang in there, it will probably get way worse before it gets better, but it DOES get better. B) The thing you have to learn is every person is an individual who will make their own choices. You can't control that no matter how hard you try. However, you can influence them if you try hard enough. Just don't take their failures as your own. And C) You have to just care about the people you care about and let them know, the rest is up to them. The best you can do is try to stay a part of their lives without enabling them and just show them a good example. If they are smart, they will see where their lives are headed and where they could be headed and maybe they will make changes in their own lives as a result.
Most of all, while dropping out of high school does hurt their potential for living a better life and close off a lot of opportunities, it isn't a death sentence. They can recover from it, although that window closes a little more each year.