| Value | Category | 
                                    
                    
                        | 0 | pre-primary | 
                                    
                    
                        | 1 | primary | 
                                    
                    
                        | 2 | secondary lower | 
                                    
                    
                        | 3 | secondary upper | 
                                    
                    
                        | 4 | higher | 
                                    
                    
                        | 8 | dk | 
                                    
                    
                        | Sysmiss |  | 
                            
            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.