| Value | Category |
|---|---|
| 0 | Less than 1 year |
| 1 | Standard 1 |
| 2 | Standard 1 |
| 3 | Standard 3 |
| 4 | Standard 4 |
| 5 | Standard 5 |
| 6 | Standard 6 |
| 7 | Standard 7 |
| 8 | Standard 8 |
| 9 | Train. after primary |
| 10 | Pre-form 1 |
| 11 | Form 1 |
| 12 | Form 2 |
| 13 | Form 3 |
| 14 | Form 4 |
| 15 | Form 5 |
| 16 | Form 6 |
| 17 | Training after secondary |
| 18 | University |
| 98 | DK |