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_21 ( decile VARCHAR, authority VARCHAR, name VARCHAR )

### Question ###
How many deciles have an Authority of state and a Name of chertsey school?

### Accurate SQL ###

SELECT COUNT(decile) FROM table_name_21 WHERE authority = "state" AND name = "chertsey school"