CAT4 is available at seven different levels of difficulty. The tests have been developed in an overlapping, progressive format and are referred to as levels A to G. Levels X and Y refer to CAT4 Young Learners.
The target year group and age range covered by the norms for each test level are shown in the table below.
| CAT4 Level | Standardised Age Group | England and Wales | Scotland | Northern Ireland |
| X | 6:00-7:11 | Y2 | P3 | Y2 (P3) |
| Y | 7:00-8:11 | Y3 | P4 | Y2 (P3 & P4) |
| Level A | 7:06-9:11 | Y4 | P5 | Y4 & Y5 (P4 & P5) |
| Level B | 8:06-10:11 | Y5 | P6 | Y6 (P6) |
| Level C | 9:06-11:11 | Y6 | P7 | Y7 (P7) |
| Level D | 10:06-12:11 | Y7 | S1 | Y8 (F1) |
| Level E | 11:06-13:11 | Y8 | S2 | Y9 (F2) |
| Level F | 12:06-15:11 | Y9 & Y10 | S3 & S4 | Y10 & Y11 |
| Level G | 14:06-17:00+ | Y11 & Y12 | S5 & S6 | Y11, Y12 & Y13 |
Schools are recommended to use the level of CAT4 shown for the year group they want to assess. This is particularly important if the school results are being combined with those from other schools for whatever reason.
