Spending per student only explains about, well, less than 20 percent of the performance variation among countries, and Luxembourg, for example, the most expensive system, doesn't do particularly well.
生均教育经费投入 对一个国家教育质量的影响 大约不足20%， 例如，卢森堡是教育投入是最高的， 但其教育效果并不太好。