Hey, Azanliz, welcome to the site and particularly to TDS. I know you are feeling really trapped and controlled right now. You want to do something and your parents don't want you to do it. I've been there on both ends of that. First as the kid and much later as the parent of the kid. It's a shitty paradigm from either end, let me tell you.
If you can step back from all the emotional family stuff for a minute and simply observe yourself objectively, what do you see? You probably see someone that wants more out of life than they are getting. Maybe from there you can ask yourself what more do I really want? Do you want more adventure, more adrenaline, more mystery? Do you want to control painful emotions? Do you want to simply feel more comfortable in your own skin? Where I am headed with these questions is to a very real middle ground that could exist for you and your parents. Rather than focusing on the issue of drugs why not focus on what is behind your drug use in the first place? Because I bet your parents would understand and relate to almost any reason you come up with.
We all like to change our consciousness from time to time. It is a worthy way to enter into doing this by truly weighing how, why, when and where. This helps you to make safe decisions and to stay healthy and balanced. Addiction and abuse are always a possibility when you have not truly developed a grounded relationship with yourself inside. Needing to always be in an altered state is not balance. So examine your own use, especially the 'why' question. You will never regret that.
As far as your parents go, they are scared for you. This fear may be based on so many things ranging from misinformation to very real facts. (I would be very afraid if my child were using inhalants). Try to at least respect the root of their fear, even if you can't agree with the ways they are choosing to deal with it. The root of their fear is love and a parent's innate sense of responsibility and protection for their children. You have up to a year left with your parents legally. What would happen if they said, "OK, you are on your own now." in less than a year? This relationship is for life--bad or good, it just doesn't go away. Do whatever is in your power to cleanse your interactions of fear and anger and mistrust and ask them to do the same.
It's not torture to be drug-free for a while. Learn from it and use what you have learned going forward--you won't ever regret time spent doing so. Ask yourself all the questions above and try to find non-drug ways to address each one. Taking care of whatever is inside that pushes a person to use compulsively allows them to use responsibly and in a healthy manner should they choose to do so.