The Trends in Mathematics and Science Study (TIMSS) study measures students’ competence based on the participating countries’ curricula. Changes in students’ TIMSS achievement over time within a country is hence of interest to educational policy and practice as they may be related to, or possibly could reflect, changes in contextual factors important for student learning.

In Norway, students’ performance in mathematics at grade 9 decreased from 2015 to 2019 as evidenced by TIMSS. Seeing how teachers’ competence and their instruction are the most proximal to students and key to their learning outcome (Baumert et al., 2010; Darling-Hammond, 2000; Klieme et al., 2009; Praetorius et al., 2018), the present study seeks to investigate whether changes in teacher variables may be related to changes in the students’ mathematics.

Teachers’ competence is shaped by their formal level of education, the degree to which they have subject specialization, and through participation in professional development (e.g. Desimone et al., 2013). Teacher competence has proven to be important for teaching quality and for the students’ learning outcome (e.g. Baumert et al., 2010; Jentsch & König, 2022): A competent teacher tends to provide high quality teaching.

Teaching quality reflects the teaching going on in the classroom (i.e. teachers’ behavior) (Praetorius et al., 2018). It is a broad concept including different dimensions that have been found to promote student learning (e.g. Pianta & Hamre, 2009). According to the framework of the Three Basic Dimensions (TBD) (Klieme et al., 2009; Praetorius et al., 2018), teaching quality includes the following three dimensions: 1) Classroom management, which is about arranging for effective learning in the classroom (e.g. managing noise and disruptions). 2) Supportive climate, in which the teacher for example shows interest in and respect for all students, gives (individual) feedback and helps connecting new topics to what has already been learned, and 3) Cognitive activation, which is about challenging the students cognitively (e.g. students are asked to reason, interpret, solve problems).

As the TBD framework captures the main aspects of teaching quality, is extensively used in Europe and in the TIMSS contextual framework (Senden, Nilsen, & Blömeke, 2021; Mullis et al., 2020; Pianta & Hamre, 2009), it is used as the theoretical background for teacher quality in this study.

However, the quality of the teaching also depends on who is taught, on the background and composition of students (Praetorius et al., 2018). The quality of the teaching may be limited by students who for instance lack basic previous knowledge, who are uninterested, or lack basic language skills.

Knowing how important teachers and their teaching are to student learning, it is plausible that changes in teacher competence, their teaching quality and limitations to teaching quality, may be related to changes in student outcome. This study hence seeks to answer the following two research questions:

1. How have teacher competence, teaching quality and limitations to teaching quality changed from 2015 to 2019?

2. What is the relation between the changes in the predictors (i.e. teacher competence, teaching quality and limitations to teaching quality) and the changes in students’ mathematics achievement from 2015 to 2019? In other words, do changes in the predictors mediate the changes in students’ mathematics performance over time?

The present study includes representative samples of Norwegian grade nine students who participated in TIMSS 2015 and TIMSS 2019 along with their mathematics teachers (Nstudents=9272, Nteachers=516). Only measures identical in the two cycles were included in the study. The following variables from the teacher questionnaire were used to measure teachers’ competence: teachers’ highest formal educational level, teachers’ subject specialization (major in mathematics and/or in mathematics education), and teachers’ participation in professional development. For teaching quality, only two of the three dimensions were included (supportive climate and cognitive activation) as classroom management was not included in both cycles. We used the student questionnaire to measure supportive climate (5 items, e.g. “My teacher is easy to understand”), and the teacher questionnaire to measure cognitive activation (6 items, e.g. “Ask students to explain their answers”). Limitations to teaching, was measured by teacher responses (6 items, e.g. “Students lacking prerequisite knowledge”). Methods of analysis Data from 2015 was merged with data from 2019, adding a dummy variable labelled Time (coded 0=2015 and 1= 2019). Then Mplus version 8 was used to estimate a two-level (students and classes) mediation structural equation model (SEM) with trend data (Murnane & Willett, 2010). The TIMSS 2019 report showed that the Norwegian grade nine students’ achievement in mathematics had declined by 9 points since the 2015 study (Mullis et al., 2020). Consequently, the unstandardized regression coefficient of the effect of Time on achievement is expected to be negative and approximately 9 points. Our question is whether the predictors (i.e., the change in teacher competence, teaching quality and limitations to teaching quality) may mediate this decline. Using teaching quality as an example, the hypothesis is that if teaching quality has declined over time, and if teaching quality has a positive effect on achievement, it may partly mediate the effect of Time on Achievement. The mediation coefficient (the indirect effect) would be negative, thus teaching quality could be said to partly “explain” (albeit, not causally) the decline in achievement. Teaching quality would then mediate part of the decline in achievement over time. Alternatively, if teaching quality has increased over time, and is positively related to achievement, the result would be a positive mediation (indirect effect). As a consequence of a positive indirect effect, one might possibly claim that the higher teaching quality “prevented” an even larger decline.

Results. Regarding research question 1, the results showed that no changes were found for teachers’ specialization and professional development. Teachers’ formal level of education, supportive climate and cognitive activation increased from 2015 to 2019. Lastly, the teachers reported about a higher level of limitations to teaching in 2019 than in 2015. The results for the second research question showed significant, positive relations from teachers’ formal level of education, supportive climate, and limitations to teaching to student achievement. However, only the increase in teachers’ level of formal education and supportive climate each had a positive indirect effect on achievement and mediated 1.5 and 2.3 points of the 9 points decline in achievement respectively. The higher level of limitations to teaching had a negative indirect effect and mediated about 6 of the 9 points of the decline. Discussion and conclusion. The incline in teachers’ level of education and teaching quality could be a result of extensive strategies implemented in Norway during the last decade, aiming to increase teachers’ competence in teaching mathematics (e.g. Ministry of Education and Research, 2015). The positive indirect effect could hence indicate a prevention of an even larger decline. The limitations to teaching, on the other hand, had a negative indirect effect, which indicates a contribution to the decline. Increased limitations to the instruction over time reflects challenges with the students who e.g. don’t speak the language, who are hungry at school and lack sleep, and who lack prerequisite knowledge. Our findings on this are in line with other studies (e.g. Wedelborg et al., 2020). The present study may contribute to the field with regards to the methodology which is robust and useful for identifying relations between changes in predictors and changes in achievement. It further contributes to practice and policy.

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