Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE Teachers (last_name VARCHAR)
TABLE: CREATE TABLE Teachers (last_name VARCHAR, teacher_id VARCHAR)
TABLE: CREATE TABLE Detention (teacher_id VARCHAR)

### Question ###
Find the last names of teachers who are not involved in any detention.

### Accurate SQL ###

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