This article explores effects of parents' and friends' behaviour in verbal
inter-actions with adolescents concerning adolescents' school achievement.
The behaviour of adolescents' partners was observed in interactions elicite
d by a plan-something-together task at first measurement of a two-year long
itudinal investigation. Grades in school and perceived school success at me
asurement points 1, 2, and 3 were included to capture adolescents' academic
achievement. Cross-sectional correlations (n=32) and longitudinal partial
col-relations (n=24-26) sewed to analyse contemporaneous associations and d
irected effects across a one- and two-year time interval. Findings confirme
d systematic influences of parents' as well as friends' behaviours on the o
bjective and subjective measures of school achievement. Patterns of effects
, however; partly depending on the type of partner in interactions. The dif
ferential effects are discussed with reference to structural differences be
tween adolescents' family and friendship relationships.