By emphasizing the other tangible benefits of high school beyond making six-figure salaries.
On the other hand, if the only communicable, tangible benefit of graduating from high school is making a six-figure salary, then why would we care whether or not graduation rates decrease?
But in reality, this is probably the wrong takeaway from the article. The article's conclusion is pretty dour:
> Salaries in the fast-food industry range from eye-popping to barely getting by
So start from the fact that these salaries are not consistent between companies and positions over time. Add to that the fact that getting yourself promoted to six-figure salary manager at a Taco Bell is probably a lot more work than graduating from high school, and then add again the fact that most high school students don't dream of being fast-food managers in the first place, and are rarely making decisions based on long-term monetary goals.
All of that together means this concern is probably not worth worrying about in the first place.