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_15 (goals_against INTEGER, club VARCHAR, points VARCHAR)

### Question ###
Which Goals against have a Club of cd castellón, and Points smaller than 24?

### Accurate SQL ###

SELECT AVG(goals_against) FROM table_name_15 WHERE club = "cd castellón" AND points < 24