Instruction is the facilitation of another's learning. Instructors in primary and secondary institutions are often called teachers, and they direct the education of students and might draw on many subjects like reading, writing, mathematics, science and history. Instructors in post-secondary institutions might be called teachers, instructors, or professors, depending on the type of institution; and they primarily teach only their specific discipline. Studies from the United States suggest that the quality of teachers is the single most important factor affecting student performance, and that countries which score highly on international tests have multiple policies in place to ensure that the teachers they employ are as effective as possible. With the passing of NCLB in the United States (No Child Left Behind), teachers must be highly qualified. A popular way to gauge teaching performance is to use student evaluations of teachers (SETS), but these evaluations have been criticized for being counterproductive to learning and inaccurate due to student bias.
In the United States what is considered the single most important factor in a child's education?
quality of teachers

Of the five original great powers recognised at the Congress of Vienna, only France and the United Kingdom have maintained that status continuously to the present day, although France was defeated in the Franco-Prussian War and occupied during World War II. After the Congress of Vienna, the British Empire emerged as the pre-eminent power, due to its navy and the extent of its territories, which signalled the beginning of the Pax Britannica and of the Great Game between the UK and Russia. The balance of power between the Great Powers became a major influence in European politics, prompting Otto von Bismarck to say "All politics reduces itself to this formula: try to be one of three, as long as the world is governed by the unstable equilibrium of five great powers."
What country emerged as the pre-eminent power, due to its navy and the extent of its territories?
British Empire

Notable modern Greek artists include Renaissance painter Dominikos Theotokopoulos (El Greco), Panagiotis Doxaras, Nikolaos Gyzis, Nikiphoros Lytras, Yannis Tsarouchis, Nikos Engonopoulos, Constantine Andreou, Jannis Kounellis, sculptors such as Leonidas Drosis, Georgios Bonanos, Yannoulis Chalepas and Joannis Avramidis, conductor Dimitri Mitropoulos, soprano Maria Callas, composers such as Mikis Theodorakis, Nikos Skalkottas, Iannis Xenakis, Manos Hatzidakis, Eleni Karaindrou, Yanni and Vangelis, one of the best-selling singers worldwide Nana Mouskouri and poets such as Kostis Palamas, Dionysios Solomos, Angelos Sikelianos and Yannis Ritsos. Alexandrian Constantine P. Cavafy and Nobel laureates Giorgos Seferis and Odysseas Elytis are among the most important poets of the 20th century. Novel is also represented by Alexandros Papadiamantis and Nikos Kazantzakis.
Who sang in a voice that is in the high octave range from the Modern Greek Era ?
soprano Maria Callas