Query Critique

I just finished a new query where I summarized detail information. I'm
wondering if I did this really awkwardly or is this a common way to
write SQL? I've cross referenced the end results and the data seems
consistant, so I am happy with the results.
TIA

SELECT
SESSION_ID,
CAMPUS_ID,
SUM(STUDENT_COUNT) AS STUDENT_COUNT,
SUM(NEW_STUDENT) AS NEW_STUDENT_COUNT
FROM (
SELECT
SESSION_ID,
STUDENT_ID,
CAMPUS_ID ,
STUDENT_COUNT ,
STUDENT_STARTING_SESSION_ID,
NEW_STUDENT = CASE WHEN SESSION_ID=STUDENT_STARTING_SESSION_ID
THEN (1) ELSE (0) END
FROM (
select
SESSION_ID,
STUDENT_ID,
CAMPUS_ID ,
STUDENT_COUNT ,
STUDENT_STARTING_SESSION_ID
FROM
(
select
SESSION_ID,
STUDENT_ID,
CAMPUS_ID = (SELECT STUDENT_CAMPUS_ID FROM
D_BI_STUDENT WHERE A.STUDENT_SKEY=D_BI_STUDENT.STUDENT_SKEY) ,
STUDENT_COUNT = DAY0_CLASS_COUNT,
(select student_starting_session_id from
f_bi_student_statistics where A.student_id =
f_bi_student_statistics.student_id) as 'STUDENT_STARTING_SESSION_ID'
from f_bi_registration_tracking_summary A
) AS X
WHERE STUDENT_COUNT > 0
GROUP BY SESSION_ID, STUDENT_ID, CAMPUS_ID, STUDENT_COUNT,
STUDENT_STARTING_SESSION_ID
) AS Y
) AS Z
GROUP BY SESSION_ID, CAMPUS_ID