Is there a correlation?
Most research agrees that there is a positive correlation between academic self-concept and academic achievement. Social psychologist Albert Bandura and his colleagues, however, noted that perceived self-efficacy is a stronger predictor of academic achievement than is self-concept of ability. When considered with our definitions, this means that Bandura believes that situation dependent self-evaluations play more of a role in academic achievement than overall academic concept.
Bandura and colleagues aside, most studies have revealed that self-esteem (and thus academic self-concept) is directly correlated to school performance. Trends show that students who rate themselves with a low level of overall self-esteem have poorer levels of achievement in schools than students with either a positive rating of self-esteem or a baseline measure. There is also evidence for the effect of prior academic self-concept on subject interest but the correlation between academic self-concept and achievement is greater than the correlation between prior academic interest and achievement in that area.
Bandura and colleagues aside, most studies have revealed that self-esteem (and thus academic self-concept) is directly correlated to school performance. Trends show that students who rate themselves with a low level of overall self-esteem have poorer levels of achievement in schools than students with either a positive rating of self-esteem or a baseline measure. There is also evidence for the effect of prior academic self-concept on subject interest but the correlation between academic self-concept and achievement is greater than the correlation between prior academic interest and achievement in that area.
Causality: Which comes first?
With the understanding that there IS a relationship between academic self-concept and academic achievement, we now need to understand what exactly that relationship is. This presents us with a "which came first - the chicken or the egg?" situation. If we seek to develop an overall theory of causality considering the majority of research in this area, we must conclude that the relationship is a reciprocal one. In other words, academic self-concept is both a cause AND an effect of academic achievement and thus academic achievement is also both a cause AND an effect of academic self-concept. It is further possible that the causality self-concept and achievement is developmentally dependent. Herbert Marsh and colleagues suggest that academic self-concept drives achievement in the early stages of education but becomes reciprocal in adolescence followed by a stage where academic achievement drives self-concept.
Trends in academic self-concept
In addition to Marsh's theory of causality changes over time, there is evidence for changes in both academic self-concept and academic achievement over time. Bieke De Fraine and collaborators observed the decline of academic self-concept with adolescent age but the increase of academic achievement along the same time scale. For further investigation, see De Fraine 's Fig.2 and Fig.3 reproduced below (DeFraine, 2007, p. 143):
Following adolescence, Marsh observes that academic self-concept levels out and then increases though adulthood. This is consistent with and extrapolates on DeFraine's findings. Finally, there is also evidence that the association between academic self-concept and academic achievements decrease with age (See Fig.4 from DeFraine below). Perhaps this represents the end of the reciprocal phase and movement towards the phase where academic achievement drives academic self-concept.