Knowledge and skills in Swedish comprehensive school during 40 years: A reassessment of the evidence based on the IEA studies

The IEA studies have been the major source of information about the level of achievement in the Swedish comprehensive school, which was implemented in the early 1960s. However, in the paper it is argued that the officially reported pattern of achievement is partially misleading, in that the level of achievement is underestimated in the studies conducted prior to 1995, while in the later studies achievement is somewhat overestimated. This is because schooling influences achievement more strongly than age, and in the early IEA studies age-based population definitions were used which caused the Swedish students with a comparatively high school start age to have fewer years of schooling than students in most other countries. A mathematical model is developed to adjust for the effects of this. The results from application of this model shows that the level of achievement of Swedish students was at a high international level in science and reading in the early 1990s, while after 1995 achievement has declined to a level close to the international mean.