SELECT t.StudentDimKey,
COALESCE((t.TESTA +t.TESTB)/2,t.TESTA,t.TESTB) AS [Value]
FROM
(
Select S.StudentDimKey, 
(select ISNULL(R.Score, NULL) from CLT_StudentAssessmentRawFact R, CLT_LessonPlanDim L where L.LessonPlanKey = 1 and L.LessonPlanDimKey = R.LessonPlanDimKey and StudentDimKey = S.StudentDimKey) as TESTA,
(select ISNULL(R.Score, NULL) from CLT_StudentAssessmentRawFact R, CLT_LessonPlanDim L where L.LessonPlanKey = 2 and L.LessonPlanDimKey = R.LessonPlanDimKey and StudentDimKey = S.StudentDimKey) as TESTB
from CLT_StudentPlacementFact P, CLT_StudentDim S, CLT_ClassHierarchyDim H, CLT_StudentClassFact C
where P.StudentDimKey = S.StudentDimKey
and H.ClassHierarchyDimKey = C.ClassHierarchyDimKey
and S.StudentDimKey = C.StudentDimKey
and S.StatusCode = 'A'
and S.CurrentRecord = 1
and S.SchoolID = 87577)t