| Value | Category | 
                                    
                    
                        | 6 | 6. Grade 6/Standard 4 | 
                                    
                    
                        | 7 | 7. Grade 7/Standard 5 | 
                                    
                    
                        | 8 | 8. Grade 8/Standard 6 | 
                                    
                    
                        | 9 | 9. Grade 9/Standard 7 | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.