Find the last names of teachers who are not involved in any detention.
SELECT last_name FROM Teachers EXCEPT SELECT T1.last_name FROM Teachers AS T1 JOIN Detention AS T2 ON T1.teacher_id  =  T2.teacher_id
SELECT last_name FROM Teachers EXCEPT SELECT T1.last_name FROM Teachers AS T1 JOIN Detention AS T2 ON T1.teacher_id  =  T2.teacher_id
[{'last_name': 'Brakus'}, {'last_name': 'Goldner'}, {'last_name': 'Kuhic'}, {'last_name': 'Medhurst'}, {'last_name': 'Price'}]