Massive numbers of online learners have opted to enrol in MOOC platforms such as Coursera, EdX and Udacity, where a plethora of topical courses are offered. However, a limitation of all those platforms is that they cannot effectively support teaching higher order thinking, such as critical thinking, due to logistical issues in assessing such skills. This paper discusses a pedagogically designed online system that employs a set of purposely devised techniques based on a reflexive ideology, whereby complex reasoning skills such as critical and creative thinking form part of the process. Additionally, peer- and self-reviewing together with feedback upon feedback enables scalable assessment of complex critical thinking assignments. We investigate the effect of such processes as we analyse assessment data collected from a pilot project in a single online course with just 150 students that made full use of our system, providing over 3.5 million essential data points. A pre- and post- survey also provided additional quantitative and qualitative data as we close the paper with a series of conclusions and recommendations.