In September 1883, the Korean government, under the advice of Paul G. von Mollendorff, a German advisor to the Korean court, established Dongmunhak, an interpreter school, in Seoul.It's a great misfortune that Korea has been beset by such low-quality foreign teachers for so long. It seems the first English lesson in Korea took place in 1816.
English was initially taught by two Chinese instructors who had studied in the United States and came to Korea with Mollendorff. They were soon joined by Thomas E. Hallifax, a 41-year-old Englishman who had come to Korea to establish a telegraph system but became a teacher by default.[...]
[T]he success of the school is somewhat debatable. It has been disparaged as a tool of the Chinese government (Mollendorff was appointed by the Chinese) and staffed by unqualified teachers.
Hallifax's qualification as a teacher was questioned not only by his students but by the small foreign community as well. Some described him as "agreeable, clever, and thoroughly conversant with the Far East" but others derided his checkered past noting that his "attainments were self-acquired" and he was nothing more than "a common sailor."
To be fair, Hallifax, prior to coming to Korea, had served as a sailor for only two years but had taught English part time in Tokyo for four years. Later, in 1895, he became the assistant headmaster of the Government School for Foreign Languages in Seoul ― a position he held until his death in 1908.
Obviously, he had some teaching ability but some of the Korean students felt betrayed. [...] Yi Sung-na, a former student at Dongmunhak who had quit, claim[ed] Halifax had "disgraced us (the students)."
Also worth looking at at the Marmot's Hole is this post by Robert Neff featuring text of a letter describing Seoul in 1952, as well as contemporary photos.