GCSE and A level assessments are graded examinations, where grade boundaries are set on the raw mark scale of each of the units/components comprising the assessment. These boundaries are then aggregated in a particular way depending on the type of assessment to produce the overall grades for the assessment. This article reports a simple 'sensitivity analysis' determining the effect on assessment grade boundaries of varying the (judgementally set) key grade boundaries on the units/components by +-1 mark. Two assessments with different structures were used - a tiered 'linear' GCSE, and a 6-unit 'modular' A level.