This paper summarises our research into the relationship between pupil assessment at age 14 (Key Stage 3) and participation in age 16+ education. We question whether a systematic gap between teacher-based assessment and externally marked tests indicates assessment bias or uncertainty, either in testing procedures or through teachers' perceptions of pupils' skills. We explore whether these errors have consequences for pupils' subsequent educational attainment and participation. We find that teacher and test assessments diverge slightly along lines of pupil characteristics, especially prior achievement, clearly observable to the teacher but less so to external assessors, but this does not conform to notions of teacher stereotyping. Moreover, the divergence between the assessments at age 14 has almost no bearing on pupil qualifications or participation in education after age 16, and is unlikely to influence participation rates in higher education (HE). (Contains 2 tables and 2 figures.)