The percentage of ownership of resources compared to accessing resources is a matter of policy and depends on the needs of the individual school community. The demographic and socio-economic level of the school community will determine this percentage (International Federation of Library Associations and Institutions School Libraries Section Standing Committee, 2015).
In the context of one of my casual schools, since it is a relatively small-sized school with 90 students situated in a lower socio-economic area where funding is limited, hence there are only 25 laptops and 25 iPads in the whole school. Therefore, ownership of resources is crucial for my school, however, students will be disadvantaged in accessing online resources due to shared devices, funding, and limited time to access the resources either for enjoyment, reading or assessment. Although there are subscriptions like Britannica Kids and ClickView, they are far too expensive for our school.
There are many issues regarding school library decisions on access to digital resources for a period or purchase outright, and the reliability of the platform including the ease of use. The question also asks if it is sustainable. Knowing that ownership has limits and exposure to a wide range of current material will become redundant in time, it may not be a sustainable option (Bellanti, 2019).
The balance between ownership and access will be dependent on the needs of the individual school community and rely on hierarchical leadership decisions.
References:
Bellanti, C. Q. (2019). Access to library materials in remote storage. In Access Services in Libraries (pp. 93-104). Routledge. https://www.taylorfrancis.com/chapters/edit/10.4324/9780429352034-6/access-library-materials-remote-storage-claire-bellanti
International Federation of Library Associations and Institutions School Libraries Section Standing Committee. (2015). IFLA school library guidelines. https://www.ifla.org/wp-content/uploads/2019/05/assets/school-libraries-resource-centers/publications/ifla-school-library-guidelines.pdf