SQ Q#45418892, Sql Server

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--Sql Server 2014 Express Edition
--Batches are separated by 'go'

CREATE TABLE #StudentGrades(
       StudentID int
  , CurrentGrade varchar(255)
  , SchoolEarliestGrade varchar(255)
  , SchoolID int
  , School varchar(255)
  , SchoolGrades varchar(255)
  );

INSERT INTO #StudentGrades (StudentID, CurrentGrade, SchoolEarliestGrade, SchoolID, School, SchoolGrades)
 VALUES
(7777777,   11, 'PK'    , 111   ,'Smith Elementary' ,'PK, KK, 01, 02, 03, 04, 05'),
(7777777,   11, '06'    , 222   ,'Jones Middle' ,'06, 07, 08'),
(7777777,   11, '09'    , 333   ,'Perez High School'    ,'09, 10, 11, 12');

SELECT * FROM #StudentGrades;

WITH StrCTE AS
    (
      SELECT  1 start, CHARINDEX(',' , schoolGrades) stop, StudentID, CurrentGrade, SchoolEarliestGrade, SchoolID, School, SchoolGrades
      from #studentGrades A
      UNION ALL
      SELECT  stop + 1, CHARINDEX(',' ,schoolgrades  , stop + 1), StudentID, CurrentGrade, SchoolEarliestGrade, SchoolID, School, SchoolGrades
      FROM StrCTE A
      WHERE stop > 0
    ),
   SUBCTE AS (
    SELECT StudentID, CurrentGrade, SchoolEarliestGrade, SchoolID, School, SchoolGrades, ltrim(SUBSTRING(schoolgrades , start, CASE WHEN stop > 0 THEN stop-start ELSE 4000 END)) AS stringValue
    FROM StrCTE)
    SELECT * 
    FROM SUBCTE
    WHERE currentgrade = stringValue

View schema
Execution time: 0,02 sec, rows selected: 4, rows affected: 3, absolute service time: 0,17 sec