Jonathan Ullmer obtained a distinction in teaching practice at Durham and Oxford after completing a combined study of English. He earned his master's degree from the University of Victoria, where he specialized in North American literature. He is also an honors graduate of the Institute for Arts in Education and Therapy and an LRAM-accredited Royal Academy of Music teacher.

Mr. Ullmer began his teaching career in 1985 at Swanley School in Kent, where he taught English and Drama. From 2002 to 2004, he was the Assistant Principal at Sawyers Hall College of Science and Technology in Essex, and then he was the Arts Curriculum Director at Cecil Jones High School 11-18 Foundation School in Southend until he went on to Sawyers Hall College of Science and Technology in Essex. In 2008, he was appointed Vice-Principal of CATS Cambridge College before becoming Principal in 2010.

Jonathan accepted a post as headmaster at Haileybury School in Kazakhstan's capital, Nur-Sultan, after receiving an offer from the school. Jonathan's expertise in school development made him a perfect choice for the role at the city school where he was collaborating with teachers to help Haileybury pass an inspection.

Jonathan also assisted the school in obtaining NEASC and CIS certification, preparing the institution to offer both American and international baccalaureate diplomas. Yuri Ryabov was chosen head of school in 2013, and his leadership has helped place the school on a shortlist for the Times-Independent Schools Prizes, as well as two honors for student leadership programs and Kazakh language instruction.