The following article contains an answer for the question: What was the name of the person who was teaching students by the time he was 15? , can you please find it? 

Lissitzky was born on November 23, 1890 in Pochinok, a small Jewish community 50 kilometres (31 mi) southeast of Smolensk, former Russian Empire. During his childhood, he lived and studied in the city of Vitebsk, now part of Belarus, and later spent 10 years in Smolensk living with his grandparents and attending the Smolensk Grammar School, spending summer vacations in Vitebsk. Always expressing an interest and talent in drawing, he started to receive instruction at 13 from Yehuda Pen, a local Jewish artist, and by the time he was 15 was teaching students himself. In 1909, he applied to an art academy in Saint Petersburg, but was rejected. While he passed the entrance exam and was qualified, the law under the Tsarist regime only allowed a limited number of Jewish students to attend Russian schools and universities.
Like many other Jews then living in the Russian Empire, Lissitzky went to study in Germany. He left in 1909 to study architectural engineering at a Technische Hochschule in Darmstadt, Germany. During the summer of 1912, Lissitzky, in his own words, "wandered through Europe", spending time in Paris and covering 1,200 kilometres (750 mi) on foot in Italy, teaching himself about fine art and sketching architecture and landscapes that interested him. His interest in ancient Jewish culture had originated during the contacts with a Paris-based group of Russian Jews led by sculptor Ossip Zadkine, a lifetime friend of Lissitzky since early childhood, who exposed Lissitzky to conflicts between different groups within the diaspora. Also in 1912 some of his pieces were included for the first time in an exhibit by the St. Petersburg Artists Union; a notable first step. He remained in Germany until the outbreak of World War I, when he was forced to return home through Switzerland and the Balkans, along with many of his countrymen, including other expatriate artists born in the former Russian Empire, such as Wassily Kandinsky and Marc Chagall.Upon his return to Moscow, Lissitzky attended the Polytechnic...

Lissitzky