In a subsequent step, the 15-year-old students within these schools were listed by the school coordinators. From these lists, students were randomly selected, ensuring that everyone had an equal chance of being included in the sample. Approximately 60 students were chosen from each school.

For the survey, around 36 15-year-olds were selected, i.e. students born between January 1 and December 31, 2010. The fact that some students are not exactly 15 years old at the time of the test is intentional and is handled in the same way internationally.

In addition to the 15-year-olds, two 9th-grade classes were included in the survey to enable class-level analyses. In all schools, except for vocational schools, one 9th-grade class was selected, and from this class, 18 students (regardless of age) were randomly chosen. Vocational schools were excluded as they typically do not have 9th-grade classes.

Alongside the students, teachers and trainee teachers participated in an online survey at each school if they taught a science subject (biology, chemistry, physics, or integrated sciences) or English.

The sampling of schools in Germany for the main survey was conducted by the international study coordination. For this purpose, we reported all schools of the school types where 15-year-old students are taught. The international study coordination then selected the school sample from these schools based on the distribution of school types across the federal states. The sample for the main survey included approximately 270 schools in Germany.

Based on the results of the field trial, we revised the instruments for the main PISA 2025 survey. In this process, the PISA National Center reviewed all competency tasks once more. Additionally, we also adapted the questionnaires for students, teachers, school leaders, and parents again.

As in every assessment cycle, we corrected linguistic errors and inaccuracies and excluded individual questions if necessary. The decision on whether tasks and questions were excluded or retained for the main PISA 2025 study was determined by international and national analyses of the field trial as well as content considerations.

In the final step, we approved the tasks and questions for the PISA 2025 main survey.

In the fall of 2024, after quality control checks, the international PISA consortium handed over the processed national datasets to the participating countries. The PISA National Center in Germany contributed to ensuring that all countries received comprehensive quality indicators for all tasks. From the international side, reports on the quality of the procedures were prepared for the questionnaires and all competency tests. These reports included information on the difficulty of the tasks and the reliability of the coding, among other aspects. In addition to these international evaluations, we also conducted our own analyses using the German field trial data.

Among other things, we related the nationally supplemented instruments on various aspects of learning in the digital world to the international PISA tasks in this area.

From April to May 2024, the PISA 2025 field trial was conducted at the selected schools. A total of 2,126 students at 50 schools in Germany took part.

During the field trial, we tested the questionnaires and skills tests. The focus was on scientific literacy as the main domain. We also took a closer look at the innovative domain of learning in the digital world, which was surveyed for the first time. The field trial also included a foreign language assessment to measure students' English language skills. In the areas of mathematical competence and reading literacy, we only used tasks that had already been tested in previous PISA surveys. You can find more information on the individual domains here.

The field trial serves to test both the materials and the procedures. Among other things, it was investigated whether tasks are more or less challenging in different countries. For example, different answer formats were tested for the questionnaires. We also checked that the practical implementation of the foreign language test worked as planned.

After completing the field trial, the team handed over the data from Germany to the international consortium for further processing.

Prior to the field trial, all associated materials are reviewed by the Ministries of Education and Cultural Affairs of the respective federal states in terms of content and data protection. In addition to the procedures, all letters to the groups involved (students, parents, teachers and school administrators) and the associated context questionnaires are also reviewed. The test items are not published for reasons of content. However, anyone interested can get an impression of the German items here.

The PISA study was also fully approved by the Ministries of Education and Cultural Affairs and data protection authorities of the participating federal states in advance of the PISA 2025 field test. As far as possible, we integrated the content-related feedback on the submitted materials into the field trial or noted it for the main survey. As PISA is an international comparative education study, the focus is on the comparability of the test materials across countries. When making adjustments, we pay particular attention to compliance with international standards. We ensure that comparisons with previous survey periods are possible.  

For the sampling of 15-year-old students, we first selected the schools based on the distribution of school types in the German federal states. Special education schools and vocational schools were highlighted to accurately represent their share in Germany.
Unlike the main survey, not all federal states were selected for the field test; only a small subset was chosen. We ensured that the sample included states of varying sizes and diversity. Furthermore, schools were not chosen through a statistical selection process as in the main survey, but rather based on their logistically convenient locations for conducting surveys. The field test sample for PISA 2025 included 49 schools in North Rhine-Westphalia, Hesse, Berlin, and Saxony-Anhalt.
In the next step, 15-year-old students within these schools were randomly selected, giving all students an equal chance of being included in the sample. A maximum of 64 students was selected per school.

Alongside the 15-year-olds, one 9th-grade class per school was included to enable class-level analysis. In three of these schools, an additional 18 randomly selected 9th-graders from each class participated in the survey. Altogether, the sample included 2,208 students.

In addition to students, approximately 10 science teachers (biology, chemistry, physics, or integrated sciences) and all English teachers for grades 9 and 10 at each school participated in an online survey.
For the additional domain English language proficiency (FLA), around 400 students and all English teachers were selected.

During the reconciling process, we create a single, technically accurate version from the two German translations produced in the previous step. We adapt the language to terms commonly used in Germany. Since PISA 2009, we have collaborated with other German-speaking PISA participant countries (Switzerland, Austria, Luxembourg) for this process. In a multi-day meeting, we develop a “Common German Version” of the PISA items. Colleagues from the natural sciences support us in finding formulations that are commonly used in scientific subjects in schools.

Finally, the international project management reviews the Common German Version to ensure comparability with the source version and fairness across other countries' translations. This verification takes place at the PISA contractor cApStAn in Belgium, where all translations undergo linguistic review and multiple rounds of revisions in consultation with national project teams. After this, the items for the cognitive test and the questions for the context questionnaires are ready for the field test.

From March to October 2023, two translators independently translated the new PISA items for the areas of scientific literacy, learning in the digital world, and English language proficiency, as well as the context questionnaires, from the original English or French versions into German.

We are pleased to work with such a highly skilled team and would like to extend our heartfelt thanks to:

Julia Frenzel from Hamburg
Ulrika Wiesner from Nuremberg
Franziska Klos from Munich

The preparation of test materials for PISA 2025 began in April 2022. We received units and items in several batches, which were reviewed by both external and internal subject matter experts. In the science domain, we would like to extend our special thanks to the following external experts for their support:

• Prof. Marcus Hammann (Biology Education, University of Münster)
• Prof. Alexander Kauertz (Physics Education, University of Koblenz-Landau)
• Prof. Dr. Jenna Koenen (Chemistry Education, Technical University of Munich)
• Prof. Dr. Friederike Korneck (Physics Education, Goethe University Frankfurt am Main)
• Prof. Dr. Silke Mikelskis-Seifert (Institute for Chemistry, Physics, and Technology, University of Education Freiburg)
• Prof. Knut Neumann (Physics Education, IPN Kiel)
• Prof. Mathias Ropohl (Chemistry Education, University of Duisburg-Essen)

For the innovative domain, we would like to sincerely thank Prof. Dr. Ira Diethelm (University of Oldenburg) and Dr. Michael Sailer (Ludwig Maximilian University of Munich) for their valuable input.