simplifying SQL

I have this query which essentially returns records that exist in one
table (studentclass) and not another (effortandattainment) to check when
teachers have entered their student grades.

select
distinct(studentclass.studentclassid),classes.subject,studentclass.studentid as classstudent,classes.teacher,students.studentid,students.firstname,students.surname
from studentclass left join effortandattainment
on(effortandattainment.classid=studentclass.classid and
effortandattainment.studentid=studentclass.studentid),students,classes

where students.studentid=studentclass.studentid
and studentclass.classid=classes.classid
and studentclass.classid not in (
select studentclass.classid
from studentclass inner join effortandattainment
on(effortandattainment.classid=studentclass.classid and
effortandattainment.studentid=studentclass.studentid)
)

I was wondering whether a simpler method exists to do the same thing or
is this OK.
Regards
Garry