How can I group student scores into quintile using SQL Server 2008

Question

Can anyone help me to group student scores into quintile? I think there is a feature in SQL Server 2012, but still we havent upgraded to it as we are using 2008R2. I tried

Answer 1

Borrowed from marc_s +1

DECLARE @Students TABLE (StudentID INT IDENTITY(1,1), StudentName VARCHAR(20), Score INT)

INSERT INTO @Students(StudentName, Score)
VALUES ('Student 1', 20), ('Student 2', 20), 
('Student 3', 30), ('Student 4', 30), 
('Student 5', 40), ('Student 6', 40), 
('Student 7', 50), ('Student 8', 50), 
('Student 9', 60), ('Student 10', 70), 
('Student 11', 70),('Student 12', 80), 
('Student 13', 80),('Student 14', 90)

SELECT s.StudentName, s.Score, qm.maxQ
  FROM @Students as s
  join ( select score, MAX(Quintile) as maxQ
           from ( SELECT Score, Quintile = NTILE(5) OVER(ORDER BY Score)
                    FROM  @Students ) q 
          group by q.score ) qm
    on qm.Score = s.Score