SELECT t.FirstName + ' ' + t.LastName AS FullName, s.[Name] + '-' + CAST(s.Lessons AS varchar(12)) AS Subjects, COUNT(st.StudentId) AS Students
    FROM Teachers AS t
    JOIN StudentsTeachers AS st ON st.TeacherId = t.Id
    JOIN Subjects AS s ON s.Id = t.SubjectId
    GROUP BY t.FirstName, t.LastName, s.[Name], s.Lessons
    ORDER BY Students DESC