Formative student assessment data have the potential to help teachers improve their instruction by offering objective data to supplement the teacher’s subjective intuition and professional judgement. This study investigates the “bottom-up” implementation of a data informed evaluation culture in public schools in two Danish municipalities.

The intervention consisted of two parts. First, a digital learning tool was made available to the teachers. The tool works as a two-sided platform and consists of a game (played by the students) and a student learning report. The data for the student learning reports are generated through three steps: 1) the teacher's formulation of relevant questions for the students to answer in the game, 2) collection of data through students' playing the game, and 3) visualization of the data in student learning reports (based on Item Response Theory) made available to the teacher immediately after the game. Second, the teachers participated in a training program in which the learned how to use the data from the digital learning tool in their everyday practice.

The purpose of the paper is to examine behavioral changes to the teachers' data use by analyzing longitudinal mixed methods data. Specifically, I investigate the degree to which teachers develop a data-informed behavior regarding three aspects of their practice: feedback to students (and parents), optimizing and adjusting instruction and collaboration in PLC's during the intervention.

The paper draws on a longitudinal mixed methods design in which digital data from a digital learning tool used by teachers is combined with quantitative data from a survey and qualitative data from focus group interviews with (the same) teachers. Data is collected three times during the intervention period, providing a longitudinal perspective. The total data set consists of 96 teachers in 11 schools in two municipalities in Denmark which was collected from August 2017 to June 2018. The quantitative data is analyzed by means of descriptive statistics and combined with results from a qualitive content analysis of the qualitive data.

Preliminary results show that 1) teachers are reluctant to use data for several reasons and talk about an actual "data overload" in these years, 2) they lack the competencies to act didactically on the information that data can provide them with, 3) when there is a mismatch between data and their subjective assessment of a student, they look for individual or technical explanations, which may explain why the data is "wrong", and 4) teacher teams in their current form in Denmark do not have the organization, competencies and time to capitalize of detailed student data.

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