This study focuses on processes involved in students' academic self-concept constructions before, during, and after secondary school transition. The study is based on a four-wave longitudinal dataset (N = 1953). Structural equation modeling showed that during school transition, the impact of grades on students' academic self-concepts in Math and English decreased whereas the effects of maternal competence perceptions increased. After the transition, the effects of grades increased, while the effects maternal competence beliefs decreased again. The results are interpreted in terms of differential emphasizing of sources of information for students' self-concept construction. During school transition, elementary school grades lost informational value for self-evaluations due to the changed frame of reference. To secure stable and valid self-assessments, students emphasized other sources than grades; in this, case information obtained through parental competence appraisals. After transition, when valid grades were available for the students' constructions again, the temporarily heightened parental influence decreased again. (Contains 5 tables, 1 figure, and 2 notes.)