|Subgroup      |   N| Median| IQR_lo| IQR_hi|
|:-------------|---:|------:|------:|------:|
|Reading       | 161|  -0.09|  -0.15|  -0.02|
|Mathematics   | 128|  -0.17|  -0.23|  -0.10|
|Primary       | 196|  -0.12|  -0.19|  -0.05|
|Secondary     |  95|  -0.12|  -0.21|  -0.06|
|High income   | 283|  -0.12|  -0.20|  -0.05|
|Middle income |   8|  -0.37|  -0.64|  -0.31|
