Why don't public schools teach this?

"But it typically is personal failure and social dysfunction that create poverty. To stay out of poverty in America, it's necessary to do three simple things, social scientists have found: finish high school, don't have kids until you marry, and wait until you are at least 20 to marry. Do those three things, and the odds against your becoming impoverished are less than one in ten. Nearly 80 percent of everyone who fails to do those three things winds up poor." - Steven Malanga