The establishment of international testing regimes such as the Progress in International Reading Literacy Study (PIRLS), the Trends in International Mathematics and Science Study (TIMSS), and the Programme for International Student Assessment (PISA) has provided one way for individual countries to monitor the effectiveness of their educational systems. Not only do such programs allow for overall student achievement to be compared across member, and partner, countries of the Organisation for Economic Co-operation and Development (OECD), and to those countries choosing to participate in PIRLS and TIMSS, but comparisons can also be made in relation to the percentage of students achieving at or below the minimum standards for literacy and numeracy. Studying the educational organisation of those countries and economies in which high-ranking results in international testing have been produced, and in which a lower percentage of students achieving minimum standards in literacy and numeracy is evident, provides valuable information for use in countries where there is a desire for improved student performance, especially for lower achieving students. In combination with the research literature, the main findings from an investigation of the roles played by teachers, students and systems suggest that it is teachers who make the difference, and that it is the responsibility of governments and teacher training institutions to select and prepare teachers accordingly.