-- Database schema
| list : LastName [ TEXT ] primary_key , FirstName [ TEXT ] , Grade [ INT ] , Classroom [ INT ] | teachers : LastName [ TEXT ] primary_key , FirstName [ TEXT ] , Classroom [ INT ] |
-- -- Find the last names of the teachers that teach fifth grade.

SELECT DISTINCT T2.lastname FROM list AS T1 JOIN teachers AS T2 ON T1.classroom  =  T2.classroom WHERE grade  =  5;