According to the International Baccalaureate MYP: From principles into practice (Updated 2022 for use with the latest Programme standards and practices), Service as Action is:
"Service requires that students are able to build authentic connections between what they learn in the classroom and what they encounter in the community. When connected to classroom learning, the experience of service offers opportunities to apply concepts, skills and knowledge. Students explore the community in its complexity as they gain personal insight and become more confident and responsible. Through service as action they become “actors” in the “real world” beyond school." (23)
"Service activities should evolve beyond doing for others to engaging with others in a shared commitment towards the common good. Meaningful service requires understanding of an underlying issue such as poverty, literacy or pollution, and authenticating the need for this service. Meaningful service includes interaction, such as building links with individuals or groups in the community. To align with the general principle that the rights, dignity and autonomy of all those involved in service are respected means that identification of needs towards which a service activity will be directed has to involve prior communication and full consultation with the community or individual concerned. This approach, based on a collaborative exchange, maximizes the potential benefits for all the people involved, including learning opportunities for students as they develop and strengthen communication abilities." (23)
Simply put... Service as Action is:
Service is to make a positive difference in the lives of others and in the environment; and action is to learn by doing.
In the context of ISSR, this means that service is achieved by addressing and justifying a need (Learning Outcomes), and the action is achieved by showing learning (approaches to learning (ATLs) and Learner Profile)
According to Further guidance for developing MYP service as action:
Action is learning by doing and experiencing, and is a key component in constructivist models of education, including the kind of teaching and learning common to all IB programmes. Through responsible action, tightly connected with sustained inquiry and critical reflection, young people and adults can develop the kinds of attributes described by the learner profile that are essential for success in future academic pursuits and life beyond the classroom.
Service, as a subset or particular kind of action, has always been a shared value of the IB community. IB learners strive to be caring members of the community who demonstrate a personal commitment to service, and act to make a positive difference to the lives of others and to the environment.
Service as action: With appropriate guidance and support, MYP students should, through their engagement with service as one of the significant forms of action, meet the learning outcomes to develop the skills and attributes of an IB learner. IB World Schools value service with others as an important way to engage in principled action across a range of overlapping local and global communities. (2)
If you need a simple overview, see the following slides presentation: