There is recognition that students need to be equipped with appropriate social and cognitive skills demanded by the workforce. The unresolved question is how to do this. Many education systems globally are addressing this demand by including skills such as critical thinking, problem solving, collaboration, and creative thinking into curriculum documents or supplementary materials. However, there is little research which identifies an evidence basis for successful integration. An integrated approach to teaching the skills across domain areas is necessary for sustainability. Traditional methods of assessment may not be sufficient, and innovative methods need to be sought and validated. Teachers require professional development, resources and tools to be effective. This presentation outlines an approach to develop an assessment framework for measuring and monitoring 21st century skills in the classroom. Research findings will highlight how assessment data has improved understanding of the skills, how these develop, and what we can do to enhance the skills.