According to research, peer assessments in education can significantly contribute to the learning experience of pupils through establishing motivation, confidence and essentially dynamic higher order learning skills. This inquiry specifically focussed on exploring the role of success criteria within peer assessment as an effective learning tool for pupils. The research comprised of a group of 30, year 7 science pupils from an Ofsted rated “outstanding” school. Research findings support the use of success criteria as an effective learning tool, so long as it is used correctly. It suggests that the efficacy of success criteria is dependent on its transparency, rigidity and explicitness. The findings from the study reveal that pupils are more likely to connect with their cognitive and intellectual processes to reach suitable judgements in the absence of rigid, explicit success criteria – and that the use of broader guidelines is more appropriate, to enhance and guide the learning of pupils.