'Your performance is '+grade

CREATE TABLE dbo.x
(
 Id_student INT,
 Id_subject INT,
 grade VARCHAR(10)
)
INSERT  INTO dbo.x
        (Id_student, Id_subject, grade)
VALUES  (1, 1, 'Good'),
        (1, 2, 'Fair'),
        (1, 3, 'Poor'),
        (1, 4, 'Good'),
        (1, 5, 'Fair'),
        (1, 6, 'Poor');

SELECT  Id_student,
        'Your performance is ' + grade + ' in ' + GroupConcatTest.dbo.group_concat(Id_subject) AS [Statement]
FROM    dbo.x
GROUP BY Id_student,
        grade;

SELECT 'Your performance is ' + CONVERT(Varchar, grade);