Researchers, policymakers and society at large seem to agree that summative assessments such as grading and testing affect students´ learning and achievement in school. In several reviews on the impact of summative assessments on students´ learning, motivation and achievement, it has been shown that low-achieving students are negatively affected by high-stakes testing and grading (Harlen & Deakin Crick 2002; Natriello 1987), that some students experience test-anxiety (Harlen & Deakin Crick 2002), and in many cases, students would learn more if not being assessed in high-stakes summative environments (Black & Wiliam 1998; Crooks 1988; Kluger & DeNisi 1996). In two previous studies, summative assessment (grading) was found to have a differentiating effect on students´ subsequent achievement in school where grading in 6^th Grade affected low-achieving students´ subsequent achievement negatively, compared to ungraded low-achieving students (Klapp, Cliffordson & Gustafsson, 2014; Klapp, 2015). The differences between low-achieving graded and ungraded students were significant with Cohen´s d .31. The difference between graded and ungraded high-achieving students was negliable with Cohen´s d .14. Students´ level of achievement was measured by cognitive tests.

One possible explanation for the negative grading effect may be that students´ non-cognitive or affective skills such as self-concept and motivation are affected by summative assessment regimes (Wentzel et al. 2010) and thus affect their learning and achievement in school (Harlen & Deakin Crick 2002). New information (grades) may thus have affected the low-achieving students negatively.

The Conservation of Resource Stress theory (COR) (Covington 2000; Frydenberg 2008; Hobfoll 1989, 2001) is an overall multi-disciplinary theory which builds upon the beliefs that humans are trying to keep, develop and gain personal resources in order to manage in difficult situations and throughout life. For students in school, resources are personal cognitive and non-cognitive skills such as academic and social self-concept, interest and motivation. When students´ resources are threatened, for example by failure in learning situations, in summative assessment situations and receiving bad school results, the loss of personal resources may cause emotional stress. The stress may in turn lead to negative and maladaptive learning strategies in order to avoid further losses and disparagement of school-work (Frydenberg & Lewis 2009).

In sum, literature suggests that constructs such as academic and social self-concept and motivation may be of importance for understanding why low ability students are negatively affected in their achievement when graded compared to low ability students who are not graded. It also seems as if there are differences regarding gender and socio-economic status and achievement.

Design of the study

Due to a unique natural circumstance, municipalities in Sweden could decide whether or not to grade their students in 6^th Grade which made it possible to apply a quasi-experimental design. In the sample, 50 percent of the students were graded in 6^th Grade while all students were graded in 7th Grade. By adding questionnaire data to the previous models (Klapp et al., 2014; Klapp, 2015), it was possible to investigate the importance of students´ academic and social self-concept and motivation to improve in order to explain the negative grading effect on low-achieving students.

Purpose

The purpose of the study was to investigate if academic and social self-concept and motivation to improve in academic school subjects mediated the negative effect of summative assessment (grades) for low-ability students´ achievement in compulsory school. Differences between subgroups of students (cognitive ability, gender and socioeconomic status) were controlled for in the analyses.

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