What is the 'КТ УЧЕНИК' button?

The button 'КТ УЧЕНИК' likely indicates the user's role within the platform. 'КТ' likely stands for 'Классный руководитель', meaning 'Class Teacher' or 'Form Teacher', and 'УЧЕНИК' means 'Student'. The button visually indicates that the user is currently viewing the application as a student.