Science education plays a key role in promoting Education for Sustainable Development (ESD) through the training of informed and participatory citizens committed to the management of our planet and its resources. This work presents the design and assessment of an In-Service Teacher Education Program (ISTEP) through an Educational Design Research approach aiming at developing skills that make it possible to operationalize the experimental practical teaching of science topics, within the scope of ESD, in an articulated, coherent, and progressive way throughout Basic Education. It was implemented with 14 teachers from the three cycles of Portuguese Basic Education (ages 6–15), and focused on “Soils”. An integrated set of activities and respective didactic resources were co-built (the trainer-researcher with the in-service teachers) with a progressive, systematic, and sequential vision of the “Soils” theme. The content analysis of the teachers’ answers to questionnaires and during the final reflection point to an improvement in their practices regarding the ability to plan and design didactic resources on science topics from a Sustainable Development perspective. This ISTEP can be adapted to other themes and educational contexts, namely through close cooperation on education issues, which is one of the lines of action of the Community of Portuguese-Speaking Countries.