How much education is optimal?

A new report on education in the U.S. will undoubtedly cause some to lament the "fall and decline" of the U.S. and beg the nation to spend more in our schools.  I only ask that we keep one consideration in mind.  First, note the dominance of South Korea in education (chart below).  Then read a recent article in The New Yorker about what South Korean children endure as they are pressured to out-perform each other (the government must even regulate the amount of tutoring children get).  Finally, let us remind ourselves that the most important part of education is learning how to live a happy, meaningful life.  That is a lesson South Korea has not learned.  We should find a wiser educational system by which to compare ours.