Can I move out at 18 even if Im still in high school?

Yes, since legally you are an adult in the eyes of the law, you are not required to stay with your parents if you have found/can pay for your own place.

Legally, I believe so. Or at least I don't know of a country/state that doesn't allow this. But there are definitely a lot of concerns that you might want to weigh while making this decision. How would you take care of yourself financially? If your answer is a job, than you also want to consider how you would juggle the number of hours you need to work in order to be financially independent with the time you need to make sure you graduate, and get the grades you want for yourself. You also need to consider the way this will impact your relationship with your current guardians(is. your parents, or whoever else you may be living with now). This is not to say that this isn't a good idea. It just depends on how actually terrible the situation you are in currently is, and how much you deem it worth it to disrupt the way things are now rather than waiting a number of months until you are out of high school. That's something you'll need to decide.

Yes you can the question though is should you and are you ready to do so. Moving out and being on your own may sound fun but know that being on your own means just that, you are on your own. You're responsible for the bills, your food, transportation, laundry, everything that comes with being an adult. I don't know your circumstances so I'm stating this broadly but if you have the option to remain at home in an environment to figure things out, use it because out in the "real world" everyone else is living just like you and will not be as understanding to issues you may have.