It has long been acknowledged that science skills play a crucial role in fostering economic development (Hanushek & Woessmann, 2012) and technological innovation (Varsakelis, 2006). Therefore, governments around the world are searching for ways to effectively enhance science education. Teachers and their instructional quality play an important role in student achievement and learning (Harris & Sass, 2011). It is also emphasized that teachers are one of the essential factors to enhance student skills and knowledge improvement (Harris & Sass, 2011). However, among several factors associated with students, teaching strategies, school, and home, teacher quality has an important role in student achievement.
The teacher quality framework (Goe, 2007) suggests that a teacher’s college degrees, certificates, and their test scores, among a group of inputs, can indicate who might be a successful teacher inside a classroom. However, teaching quality is not only defined by teacher certification and training but is also explained by what teachers do inside a classroom and how they teach, i.e., their classroom practices. Blömeke, Olsen and Suhl (2016) evaluated the relationship between educational input and process properties of schooling, and students’ cognitive outcomes with TIMSS 2011 data. The study revealed that teacher quality was significantly related to instructional quality and student outcome, while instructional quality was not a good predictor of student outcome.
Teacher’s knowledge of subject-matter, teaching skills, personal characteristics, and professional development have been found to be among the most effective characteristics of teachers (e.g., Toraman, 2019). However, no consensus on the essential teacher qualifications that explain students’ academic performance has been reached (Scheerens & Blömeke, 2016; Lee & Lee, 2020). Moreover, despite the emphasis on improving teaching qualifications (Goe, 2007), students from socioeconomically disadvantaged households and ethnic minorities are less likely to receive instruction from qualified teachers, since less qualified teachers are concentrated in schools and classrooms teaching students with low socioeconomic status and academic achievement (Luschei & Jeong, 2018).
Additionally, educational equity and quality are considered central points of Swedish school policy (Kelly et al., 2020). The Swedish Education Act underscores the school system’s mission of offering equal education quality, learning opportunities, and support to all students regardless of their background characteristics, and the type of schools they are attending (Swedish Education Act, 2010).
Against this background, the main objective of this study is to investigate the relationship between teachers’ experience, education, and their instructional practice, while controlling for students’ socioeconomic background and classroom SES composition. The study also aims to examine the schools’ compensatory effect of the teacher -related factors for educational equity, which is measured as the influence of home educational resources on students’ science achievements. According to the national curriculum for the compulsory school in Sweden, science is separated into the subjects of biology, chemistry, and physics. Therefore, the following research questions will be scrutinized in each of the science subjects:
1- Are teachers’ instructional practice, teachers’ experience and education, and classroom SES composition significantly related to student science achievement, controlling for students’ family background?
 
2- How do teachers’ experience and education, and classroom SES composition relate to their instructional practice?
 
3- How do instructional practice, teacher experience and education, classroom average achievement level and classroom SES composition mitigate students’ family background impact on their achievement?

The present study uses Swedish TIMSS 2019 data focusing on the science domains of biology, chemistry, and physics in the eighth grade. In Sweden, approximately, 4000 8th graders and 200 classes participated in TIMSS 2019, which are taught by an average of 3 science subject-teachers in each class. The student questionnaire variable home educational resources was used as proxy of students’ socioeconomic status (SES). Teachers’ instructional practice, teacher’s years of teaching experience, completed level of formal education, and their major area of study were also selected from the teacher questionnaire data. The choice of the specific variables is justified by previous literature, indicating the influence of the included factors on student achievement. The analysis is carried out simultaneously at student and classroom levels through two-level modelling that is used to investigate the effect of instructional practice, teacher experience, and teacher qualifications on differences in student achievement in biology, chemistry, and physics, which vary because of the provision of home educational resources. The application of multilevel analysis accounts for the potential cluster effects and allows for the investigation of the proposed research questions at the student and classroom levels. The sampling weight was used to make sure that the weighted sample matches the actual sample size in Sweden. The data management was carried out in IBM SPSS Statistics 29 and the models were estimated by Mplus 8.6 (Muthén & Muthén, 1998-2017). All five plausible values were used. The two-level modelling technique was applied in a stepwise manner: • Firstly, a Confirmatory Factor Analysis was carried out to test the validity of the construct instructional practice (IP). • Next, a random slope-only model of the relationship between students’ family SES and their science achievement in each subject was run to test whether the relationship varies across different classrooms to decide upon the choice of the final model. • If the random slope was not statistically significant, the latent variable IP was related to science achievement in a two-level random intercept model, controlling for student and class-level contextual characteristics (teachers’ experience and education, and classroom SES composition). • If the random slope was significant, the compensatory effect of class-level factors on random slope was tested by regressing the random slope on the class-level factors in a two-level random intercept and random slope model. This was to account for the cross-level interaction between students’ family SES and their science achievement.

The model fit indices suggested that the measurement model of Instructional practices fit the data well: X2(12) = 258.933, p = 0.00, RMSEA = .073 (90% CI = .065-.081), CFI = .946. SRMR = .033. Factor loading ranged from .45 to .71, indicating the measures of the latent constructs are valid and the measurement model can be established. In the second step, random-slope-only models using the five plausible values for students’ biology, chemistry, and physics achievements and home educational resources were carried out. The results showed a significant variance of the random slope indicating that the relationship between student science achievements (biology and physics) and their home educational resources vary significantly across different classrooms. Consequently, two-level random slope models using the data for biology and physics domains, and a two-level random intercept model using the data for chemistry domain were implemented. Interestingly, the results show that teachers' instructional practice has no significant influence on students’ achievement in biology, chemistry, and physics, when controlling for individual and classroom contextual characteristics. Teachers’ experience has a positively significant influence on biology achievement. However, it has no significant influence on chemistry and physics achievement at the eighth grade. In addition, teacher education and their major area of study had no significant influence on student achievement in the three domains of science. There are no significant relations between teachers’ experience, education, and classroom SES-composition and teachers’ instructional practice based on the Swedish TIMSS data. However, classroom SES-composition is a positively significant predictor of student achievement in all three domains. The results also show that teachers’ experience and their education are significantly correlated.

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