There has been a major shift in educational learning goals--as seen most recently by Goal 4.7 of the Sustainable Development Goals--focused on global citizenship education and education for sustainable development. The shift concerns recognition of the need for education systems to equip learners with competencies such as problem solving, collaboration, critical thinking, and communication. The focus on these "21st century goals" is visible in education and curricular reform, and has been promoted by global discussion of changing work and societal needs. This paper describes global, regional, and national examples of this shift, and then focuses on implementation challenges. The paper focuses most explicitly on the issue of assessment but asserts that any major reform in an educational philosophy shift must ensure alignment across the areas of curriculum, pedagogy, and assessment. The paper identifies several challenges to implementation of this educational shift. These include the need for clear understanding of the necessary skills and the need for clear descriptions of what different levels of competencies in skills might look like. The paper identifies possible assessment approaches, using examples to highlight effective strategies for assessment of the skills, while acknowledging the technical difficulties associated with "capture" of behaviors in scoring and reporting them. Following a discussion of the cross-cultural issues relevant to assessment of 21CS, the paper looks at three countries--Australia, Kenya, and the Philippines--to identify how they are approaching the assessment and teaching of 21CS in their basic education sectors. The countries' varied emphases on curriculum, pedagogy, and assessment are of particular interest as a majority of countries around the world explore how to approach these challenges. These examples lead to the conclusion that learning progression models are key to ensuring alignment through the education delivery system. [Support was provided to Brookings by Porticus.]