I'd say stay in school, but not for the reasons most people gave you above. I know you're brave and you don't care about backup plans, which is fine. You won't die from not having an education, you'll always be able to find a way out and get used to your situation. If you know IM at 15, it already means you're resourceful enough to make it in this world no matter what gets thrown at you.
But, these things come in handy. What if you want to move to a country, but the country's visas have education requirements? What if someone wants to hire you to manage some investments for seven figures a year, but the law requires you to have an education? What if IM gets you interested in some subject enough that you want to get into a uni to do research on it, but you can't because no high school. Hell, what if even one day you decide to become the prime minister?
This shit is useful, man, you never know when it might come in handy. Just do it, 1.5 years seems a lot at that age, but it's nothing.
And another reason. School keeps you motivated. It makes you get up in the morning and gives you a reason to work hard to get out of that system. Once you're completely free and alone, you might find yourself waking up at 1pm and doing practically nothing all day. Having a schedule and commitments will keep your head working faster.
