Background. Since children spend nearly 30% of their time in schools this venue is strategic for learning, promoting, and practicing health behaviours. Approximately a third of the Mexican schoolchildren have high body mass index for their age, and their lifestyle and hygiene behaviours are poor while pro-environment behaviours (PEB) are scarcely studied. Schools lack an independent course addressing health literacy and promotion of health and promotion of health behaviours, hygiene and PEB. Instead, random health topics are covered within other subjects. In response, unified, new health contents will be incorporated in the national curricula of basic education. This work reports the processes of evaluation and selection of these contents and learning resources.  Methods. Intersectoral and interinstitutional working meetings among academic, health and education stakeholders from the Ministry of Health and Education took place to (a) evaluate the current health contents and resources and (b) define new health contents and learning resources. The current learning objectives and learning resources were subject to a systematic evaluation based on a list of 10 criteria including the use of people first language and stigma-free content. The new contents proposed were based on the schoolchildren’s health condition, the Sustainable Development Goals, amendments of the Education law, and the COVID-19 and global warming emergencies. Results. The new contents comprised three main axes of study: (a) Sustainable Healthy Diets, (b) Physical Activity and (c) Hygiene and Cleaning. Each consisted of seven main learning objectives graded according to the academic cycle groups into primary grades 1°-2°, 3°-4°, and 5°-6° and one for 1°-3° grades at the secondary level. 57.9% of current health contents were adapted. A total of 228 educative resources were evaluated and three books were selected and amended for delivering the new contents. Conclusion. Since health literacy predicts health behaviours among schoolchildren and adolescents, Mexican schoolchildren’s access to adequate health education is imperative. Documenting the process of the development of new contents within the school curricula might provide valuable data to evaluate the impact of this type of health literacy national initiatives in low- and middle-income countries.