• 95 % CI for mean uplift: [+ 0.10, + 1.23 ] grades → the true average improvement is very likely positive and between a tenth and a little over one grade.
• Counts: 9 improved, 1 no change, 2 worsened. This is 75 % improving, 8 % same, 17 % worse.
On average, Year-11 students raised their GCSE results by about two-thirds of a grade compared with their mocks, and that uplift is statistically reliable. Given that the intervention occurred between mock and GCSE, this pattern is consistent with a positive impact.
• The effect size( d ≈ 0.75) is meaningful in educational terms: not tiny, and likely noticeable across a cohort.
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