Critical thinking has been identified as a very important skill by employers for the employment of graduates. A need exists to develop and assess critical thinking skills in tertiary institutions as employers have noted a gap in these skills among graduates. This skill can be developed, over time, by collaborative learning and given that student assessment, to a large extent, drives student learning this study proposed a revised assessment format: the 'partial pre-release' (PPR) assessment to attempt to cultivate critical thinking skills through collaboration. The PPR provided a pre-released case study where students had the opportunity to collaborate with peers before the assessment day. New information presented to students on the assessment day required increased depth in answering to showcase the cultivation of critical thinking skills. Quantitative data were collected over a period of two years using a survey. The PPR assessment format was found to show a statistically significant relationship between collaboration and the level of perceived depth when answering the required task. From these results, the study acknowledges the role that collaborative learning can play in cultivating a critical thinking mindset when an appropriate assessment tool is used.