How many assessment notes are there?
select count(*) from assessment_notes
How many does each teacher have?
select teacher_id, count(*) from assessment_notes group by teacher_id
List them in the descending order of number of assessment notes.
select teacher_id, count(*) from assessment_notes group by teacher_id order by count(*) desc
Show me the ids and first name of the top 3 teachers.
select t1.teacher_id, t2.first_name from assessment_notes as t1 join teachers as t2 on t1.teacher_id = t2.teacher_id group by t1.teacher_id order by count(*) desc limit 3