The American College of Sofia (Bulgarian: Американски колеж в София, Amerikanski kolezh v Sofiya; abbreviated as ACS) is among the top and most prestigious secondary schools in Bulgaria and the Balkans, based in the capital city of Sofia. The college, founded in 1860, is regarded as the oldest American educational institution outside the United States. American pedagogical methods are used and the primary language of instruction is English. The American College of Sofia is considered to be the best high school in Bulgaria. The graduating classes of 2008, 2009 and 2010 achieved the highest average grade on the Bulgarian matriculation exams and the mean scores on SAT and AP examinations are in many cases far beyond the average. Students from the college have won numerous rewards in various fields of science at national and international level alike. Founded in 1860 in the then-Ottoman Empire, it was initially a boys' school in Plovdiv established by American missionaries of the Congregational Church. By co-operating with a girls' school in Stara Zagora founded by the same people, the American College was established and moved to Samokov in 1871.