The first literary school was established in Pliska. It was most likely during this period that the Cyrillic alphabet was also created. Clement saw that the students found the Glagolitic letters difficult to write and began considering how they might be simplified. With the help of Naum and Angelarius, he simplified some of the characters, adapted those from the Greek alphabet that represented sounds also found in Bulgarian, and used Proto-Bulgarian runes for others.

Using the new script, the scholars began copying religious texts, which became easier to read and understand. Tsar Boris recognised the power that the Cyrillic alphabet could give the state and established it not only as a religious script, but also as the official alphabet of the administration.