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 table_name_20 ( goals_against INTEGER, points_1 VARCHAR, goals_for VARCHAR )

### Question ###
What is the average goals against for teams with more than 56 goals for and exactly 50 points?

### Accurate SQL ###

SELECT AVG(goals_against) FROM table_name_20 WHERE points_1 = "50" AND goals_for > 56