[Solved] Subquery returned more than 1 value in SQL Server

tblStdReg:

RegNo,Referenceno,SName,FName

 R-001,101,abc,sky

 R-002,102,sky,abc

tblAddFees:

Head Amount ClassID

Admission Fees   500 19

TutionFees         1000 19

Required Output

Class, AdmissionNo, ReferenceNo, SName,FName,AdmissionFees,TutionFees, TotalAmount

19, R-001, 101, abc, sky, 500, 1000, 1500

19, R-002, 102, sky, abc, 500, 1000, 1500

my query is

DECLARE @DynamicPivotQuery AS NVARCHAR(MAX)
DECLARE @cols NVARCHAR(MAX)
SELECT @cols= ISNULL(@cols + ',','') + QUOTENAME([Head])
FROM (SELECT DISTINCT Head FROM tblAddFees) AS Course  
   
DECLARE @qry NVARCHAR(4000)
SET @qry =
          N'
  
          ;WITH cteStudentMarksDetails
            AS ( SELECT TA.ClassID
                ,(SELECT AdmissionNo FROM tblStdReg TS WHERE TS.ClassID = TA.ClassID) as AdmissionNo
				,(SELECT SName FROM tblStdReg TS WHERE TS.ClassID = TA.ClassID) as SName
                ,(SELECT FName FROM tblStdReg TS WHERE TS.ClassID = TA.ClassID) as FName
                ,SUM(Amount) TotalAmount
                 FROM tblAddFees TA
                 GROUP BY ClassID
              )
  
          SELECT ClassID,AdmissionNo
                  ,SName
                  ,FName
                  
                  , ' + @cols + '
                  ,TotalAmount
                  
            FROM (SELECT ClassID
                         ,Head
                         ,Amount
                         ,(SELECT TotalAmount FROM cteStudentMarksDetails csd Where  csd.ClassID = sm.ClassID) as TotalAmount
                         ,(SELECT AdmissionNo FROM tblStdReg TS WHERE TS.ClassID = sm.ClassID) as AdmissionNo
					     ,(SELECT SName FROM cteStudentMarksDetails csd Where  csd.ClassID = sm.ClassID) as SName
                         ,(SELECT FName FROM cteStudentMarksDetails csd Where  csd.ClassID = sm.ClassID) as FName
                         
                 FROM tblAddFees as sm
                 ) p                 
            PIVOT (MAX(Amount) FOR Head IN ('+@cols+')) AS Pvt'
EXEC sp_executesql @qry

Showing error is that 

Msg 512, Level 16, State 1, Line 3 Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.