More doesn’t mean better—especially when it comes to more public school administrators and student achievement.

A recent article by Jay Greene also shows how that principles applies to swelling the ranks of teachers—one policy idea that was bandied about during the presidential campaign. As Greene wrote in the Wall Street Journal:

For decades we have tried to boost academic outcomes by hiring more teachers, and we have essentially nothing to show for it. In 1970, public schools employed 2.06 million teachers, or one for every 22.3 students…In 2012, we have 3.27 million teachers, one for every 15.2 students.

Yet math and reading scores for 17-year-olds have remained virtually unchanged since 1970…The federal estimate of high-school graduation rates also shows no progress (with about 75 percent of students completing high school then and now). Unless the next teacher-hiring binge produces something that the last several couldn't, there is no reason to expect it to contribute to student outcomes.

Hiring more teachers pulls at the parental heart strings because moms and dads think their children will get more individualized attention—and parents typically don’t like hearing about all the research that shows class size has done little—if anything—to improve student learning. As Greene continues:

Parents like the idea of smaller class sizes in the same way that people like the idea of having a personal chef. Parents imagine that their kids will have one of the Iron Chefs. But when you have to hire almost 3.3 million chefs, you're liable to end up with something closer to the fry-guy from the local burger joint.

As with most things in life, quality trumps quantity—and teacher quality is where the policy focus should be.