How many schools are there?
select count ( distinct school_code ) from department
What classes did each school offer?
select *, t3.school_code from class as t1 join course as t2 on t1.crs_code = t2.crs_code join department as t3 on t2.dept_code = t3.dept_code group by t3.school_code
What is the number of classes offered by each school?
select count ( * ), t3.school_code from class as t1 join course as t2 on t1.crs_code = t2.crs_code join department as t3 on t2.dept_code = t3.dept_code group by t3.school_code