| Test | Classmates | Extremely preterm | Mean difference (95% CI) | ||
| n | Mean (SD) | n | Mean (SD) | ||
| K-ABC | |||||
| MPC score | 153 | 104.1 (11.1) | 217 | 83.7 (18.0) | −20 (−23 to −17) |
| Simultaneous processing | 153 | 104.9 (11.9) | 201 | 86.7 (13.5) | −18 (−21 to −15) |
| Sequential processing | 153 | 101.9 (11.5) | 201 | 91.5 (13.4) | −10 (−13 to −8) |
| WIAT-IIUK | |||||
| Reading | 153 | 98.5 (11.6) | 212 | 80.2 (20.3) | −18 (−21 to −15) |
| Word reading | 153 | 99.6 (12.1) | 199 | 86.3 (17.3) | −13 (−16 to −10) |
| Reading comprehension | 153 | 100.6 (11.6) | 195 | 85.9 (18.3) | −15 (−18 to −12) |
| Pseudoword decoding | 153 | 99.7 (11.3) | 199 | 68.7 (15.6) | −13 (−16 to −10) |
| WIAT-IIUK | |||||
| Maths | 153 | 98.5 (15.0) | 215 | 71.2 (20.9) | −27 (−31 to −24) |
| Numerical operations | 153 | 98.0 (15.5) | 199 | 75.6 (18.4) | −22 (−26 to −19) |
| Mathematical reasoning | 153 | 99.7 (12.0) | 198 | 78.2 (18.1) | −21 (−25 to −18) |
| Maths estimation test | 152 | 6.6 (1.9) | 198 | 4.4 (2.0) | −2.2 (−1.7 to −2.6) |
K-ABC, Kaufman-Assessment Battery for Children; MPC, Mental Processing Composite; WIAT-IIUK, Wechsler Individual Achievement Test 2nd Edition.
K-ABC and WIAT-IIUK scales yield standardised scores with mean 100 (SD 15). Scores for maths estimation range from 0 to 11.