Research and policy increasingly emphasize the importance of data-informed practices in education (see for example, Schildkamp, 2019 and OECD, 2019). Despite this emphasis, the specific ways in which school leaders both engage with data in practice and support teachers in doing so remain underexplored. As key actors in shaping school practices and driving improvement, school leaders play a central role in interpreting and implementing data-driven initiatives. However, implementing data-informed practices requires that school leaders balance accountability demands with efforts to foster professional development and enhance teaching and learning (Datnow and Park, 2002). This underscores the need for research into school leaders’ involvement in and support of data use in local schools and the reasoning behind their practices.

Data in schools manifests in various forms, ranging from quantitative and measurable metrics that provide a clear overview of performance and wellbeing (Laursen, 2024) to qualitative data on students’ interactions, perceptions and learning processes. Both categories of data support evidence-based strategies to improve student learning and wellbeing (Laursen et al., 2024). Quantitative data however often serves as a cornerstone for accountability, enabling school leaders to demonstrate outcomes and meet external expectations. In contrast, Qualitative data plays a critical role in promoting reflective practices and professional development and guiding pedagogical improvements. In this paper, we empirically explore how these different forms of data influence school leadership practices via a multi-case study in a Danish school setting. Rather than adhering to a rigid definition of data, we examine how school leaders engage with various data types and the underlying reasoning that shapes their use.

Denmark is a compelling case for exploring school leadership’s engagement as Danish schools have been heavily influenced by the accountability elements embedded in large-scale assessments, which emphasize a quantitative data approach. Concurrently, inspired by the ‘What Works’ movement (Krejsler and Moos, 2021) and particularly the work of Hattie (2008) and Robinson (2011), Danish policies have stressed the importance of data use in schools to enhanced professionalism (SFI, 2017). Danish school leaders have largely adopted this dual approach, which highlights both the need for measurable outcomes and a focus on evidence-based professional practices.

In this context, this study draws on three compelling qualitative case studies to explore how school leadership works with data. Using an exploratory approach, the study seeks to answer the research question: How does school leadership work with data in primary and lower secondary schools?

By addressing this research question, the study contributes to the educational administration and leadership literature with empirical, in-depth insights into how school leaders themselves work with data and their reasoning behind it. Specifically, the findings demonstrate that quantitative data is essential for school leaders to communicate school results to external administrators and maintain accountability toward teachers. Simultaneously, qualitative data plays a critical role in supporting professional development, fostering reflective practices, and improving student learning.

Within this context, the study draws on empirical material from three distinct single-case studies (Yin,2009). Through discussions within our research group, we identified significant similarities across the cases. This prompted a review of our diverse data sources, leading to the synthesis of this empirical material into a single-case study. Merging the cases offers an opportunity to reanalyze the empirical data with a fresh perspective. The focus of this study is to examine how school leaders engage with data and the reasoning behind their data-driven approaches—an aspect that had not been fully explored in the original studies. Furthermore, combining the data from different cases enables us to construct a robust single-case framework, allowing for the identification and analysis of patterns of similarities and differences in how school leaders engage with data. Thus, merging cases provides a strong foundation for understanding how school leaders’ work with data and their underlying reasoning are constituted within the context of Danish schools. The tree cases – variation and similarities The original purpose of Case 1 was to adopt an institutional approach to study how school administrators and leaders translated a vision of data-driven practice into their schools. This case had an explicitly data-oriented focus. Case 2 focused on the implementation of a mandatory learning management system (LMS) and its influence on school practices. Although data usage was not the primary focus, data-related visions and practices emerged as secondary themes in both policies and interviews, tied to the LMS implementation. Case 3 aimed to explore the role of school leadership in fostering student learning and well-being. In this context, data-driven approaches surfaced as a key element during the interviews, highlighting the role of data in leadership strategies. Across all three cases, the municipalities played a pivotal role in driving the schools’ implementation of data-use initiatives. Even in Cases 2 and 3, where data was not the explicit focus, reviewing related policies and interview data revealed that municipality-driven data approaches influenced school practices. This aligns with broader nationwide policies such as the national test system, student plans, and goal-directed teaching. Consequently, state policies translated into municipal and administrative agendas, reflecting an effort to achieve both school improvement and accountability.

The study's findings highlight how school leadership teams work with data and their reasoning behind these practices. In line with the literature (e.g., Schildkamp, 2019), our analysis reveals that school leaders engage with both quantitative- and qualitative data. The use of quantitative data is motivated by dual considerations: leaders require such data to communicate school results to municipal administrators, which in turn necessitates that teachers provide leaders with hard data about their classes. However, this data is primarily generated externally, such as through the national test system and the national well-being survey. Within this context, leaders utilize their leadership teams to reflect on the hard data and make informed, professional decisions. Our study also shows that leaders’ reasoning for working with soft data is similarly dual-motivated, although for different reasons. Leaders aim to encourage teachers to engage in professional learning communities where data usage forms the foundation of their work. In this approach, data is broadly understood and may include, for example, professional reflections on student art projects. The findings highlight the need to expand theoretical frameworks of data-driven leadership to account for the interplay between quantitative- and qualitative data in decision-making. By demonstrating how leaders navigate external accountability demands alongside internal professional development goals, this study challenges traditional, binary views of accountability. The findings also suggest that fostering teacher engagement with concrete data in professional learning communities can enhance reflective practice and promote professionalization in teaching. Practically, schools should develop policies and tools that enable a balanced approach to using hard data for external reporting and soft data for internal development. Furthermore, equipping leadership teams with the skills to interpret and integrate these different types of data could strengthen decision-making and foster collaboration within schools.

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