The Abitur diploma permits successful students the admission to any German university in almost any department.

Mathematics, geometry, chemistry, physics, biology, computer science and German classes are instructed in German, while history, geography, civic education, military sciences, religion, philosophy, literature, physical education, art and music are taught in Turkish.

German and English are the compulsory foreign languages taught at Istanbul High School.

Biology is the first science class followed by physics and chemistry in the ninth and tenth grades (second and third years, respectively).

In the German Department student grades are evaluated on a 15 scale: Mehmet Nadir Bey, a retired Captain of the Navy, a prominent mathematician and teacher, together with Selanikli Abdi Kamil Efendi, a school principal, founded in 1882 the first private school in Istanbul, the Şems’ül Maarif (The Sun of Education), but for unknown reasons the partnership did not last long.

Mehmet Nadir Bey established his own private school Numune-i Terakki (The Example of Progress) in 1884, which would be the foundation of İstanbul Lisesi.

In an interview to a newspaper in 1891, Mehmet Nadir Bey would express his pride to have established the first private high school in Turkey.

İstanbul Lisesi was a 5-year boarding school charging tuition, and was admitting students following an examination.

The physical education teacher of the school, Abdurrahman Roberson, established İstanbulspor and a boy scout group in 1912.

Also in 1912, during the First Balkan War, about 30 students volunteered for the defense of the capital against the advancing Bulgarian army.

Following the closing of the foreign schools in Istanbul due to the beginning of the First World War, İstanbul Sultanisi was moved to the buildings of the Saint Benoit High School [fr; tr], and some parts of the buildings were changed to dormitories.

The curriculum was similar to Galatasaray High School, only the foreign language was German instead of French.

As the school was given only 2 days to evacuate the building by the commander of the occupying forces, most of the valuable library and the educational material had to be left behind.

Nonetheless, the faculty was still very strong and many of the teachers, such as Hasan Ali Yücel, Mazhar Nedim, Memduh Şevket Esendal, would become the prominent figures and/or leaders that contributed to the shaping of the society, ideological basis, and the governance of the Republic of Turkey.

Some of the students and many alumni would join Atatürk in his struggle for independence at very early stages, and some would lose their lives during the battles.

On Atatürk’s instructions, the school moved to the building of the former Düyun-u Umumiye (Council of Ottoman Revenues and Debts Administration) in 1933.

It incorporates the first letters of İstanbul Sultanisi, elif and sin in Arabic, a rose, the star, and the crescent.