Pupils’ grades in school are affected by several factors, including mental ability and classroom be-haviour. The aim of the present study was to explore any age-related differences in classroom be-haviour and academic skills with respect to higher or lower mental ability and gender among 6–11-year-old pupils (n=194) in a Swedish school setting. Raven’s matrixes were used, and ANOVAs were carried out. There were differences in teacher ratings in Swedish and Mathematic, partly ex-plained by interaction effects. There were significant differences between the measurement points. The high ability pupils´ lower teacher ratings in Mathematics, may depend on underachievement
