Error Code 207

I am getting the 207 error code and can't figure out the problem. I have a coldfusion page that is calling a stored procedure. The page allows users to sort the displayed columns and it is passing the column numbers into my stored procedure. I am using a case statement to decide which sort to use.

The error message is: Invalid column name 'SCHOOL'.
I've tried adding single and double quotes here and it worked before I added the case statment when I just type 'order by school'.

Below is some of my code:

SELECT P.NAME,
P.ASORG,
P.MAILSTOP,
P.OFCPHONE,
R.EMPLID,
SCHOOL = S.DESCR,
R.DEGREE_LEVEL,
R.DISCIPLINE,
TEAM = T.TEAM_NAME,
NAT_EVENT = NE.EVENT_NAME,
R.SCHOOL_CODE,
R.TEAM_CODE,
R.EVENT_CODE,
FROM HR_EXTRAS..RECRUITERS R,
HRWH..PS_SCHOOL_TBL S,
HRWH..PERSON P,
HR_Extras..UP_TEAMS T,
HR_Extras..UP_NATIONAL_EVENTS NE,
WHERE R.SCHOOL_CODE = S.SCHOOL_CODE
AND R.EMPLID = P.SNL_ID
AND T.TEAM_CODE = R.TEAM_CODE
AND NE.EVENT_CODE = R.EVENT_CODE
ORDER BY CASE WHEN @.SORT = 1 THEN P.NAME
WHEN @.SORT = 2 THEN P.ASORG
WHEN @.SORT = 3 THEN SCHOOL
WHEN @.SORT = 4 THEN T.TEAM_NAME
WHEN @.SORT = 5 THEN NE.EVENT_NAME
END

Can anyone offer suggestions?WHEN @.SORT = 3 THEN S.DESCR-PatP|||WHEN @.SORT = 3 THEN S.DESCR

That doesn't work because the SQL statement is actually part of a union query. The previous statements pull the exact same data but have

SCHOOL = ' NM-Not Assigned',

and

SCHOOL = ' CA-Not Assigned',

Sorry I didn't include that previously. The two values above are not stored in the PS_SCHOOL_TBL, thus the explicit call.|||deleted comment