I don't know how it is setup by default, but for us we store it as a custom field on our student table as "kp_student_email" so this simplified query would pull that info for us:
select student_number, lastfirst, ps_customfields.getstudentscf(id, 'kp_student_email') as email from students
I doubt you use the same name for your student email custom field :P , so you should be able to look at kid that has a student email in DDA to find out the field name used for his email. Worst case scenario, you can use this query to find some possible names for the custom field you're using:
select name from fieldstable where lower(name) like '%email%'
Then try running my original query a few times while replacing "kp_student_email" with some of your best guesses from the second query.
-Jordan