I got baked virtually every day of my Junior and Senior years of high school and my grades were fine. The people I saw getting bad grades has no ambition to get a higher education, so high school didn't matter to them. A lot of the "dumbasses" who got bad grades and barely graduated, are now running million-dollar companies and pulling 6 figures per. Home life plays a factor, but the goals and expectations which come from the parents are just as important.