Arteezy have confirmed this information at his stream.
Quote from Reddit:
"I honestly don't understand his decision, and this is coming from someone currently pursuing his PhD.
Why the f**k would any 18-year-old kid on the top of professional DotA quit to finish up high school? DAMN! Focus on DotA for now while you have a top team for a couple of years and then, once you are 20, retake your exams.
Education is always gonna be there for you and I'm sure in a country like Sweden you can access high-school when you are 20 or 21. This might be annoying but he should be taking advantage of his DotA career while it's still there.
Also he could always earn a lot of money playing DotA and pay a private university when he retires LOL. What if in one year he's not able to join a top tier team? As RTZ said, you are only as strong as your team".