For the first time, the OECD Future of Education and Skills 2030 project conducted comprehensive curriculum analyses through the co-creation of new knowledge with a wide range of stakeholders including policy makers, academic experts, school leaders, teachers, NGOs, other social partners and, most importantly, students. This report is one of six in a series presenting the first-ever comparative data on curriculum at the content level summarising existing literature, examining trends in curriculum change with challenges and strategies, and suggesting lessons learned from unintended consequences countries experienced with their curriculum reforms. Schools are constantly under pressure to keep up with the pace of changes in society. In parallel, societal demands for what schools should teach are also constantly changing; often driven by political agendas, ideologies, or parental pressures, to add global competency, digital literacy, data literacy, environmental literacy, media literacy, social-emotional skills, etc. This 'curriculum expansion' puts pressure on policy makers and schools to add new contents to already crowded curriculum. This report aims to support reflecting on questions such as 'how to avoid creating a ‘mile wide – inch deep’ curriculum?' and 'how to shift a paradigm to curriculum centred around student well-being?' It also discusses the trade-offs tied to design choices.