In French-speaking Belgium, about 4% of the children are retained in kindergarten. What are the pupils’ characteristics and the school context variables predictive of the retention in kindergarten? What are the pathways in primary education of “retained” pupils compared to their peers who started 1st grade “on time”? How can this early retention be explained? A broad database with entire cohorts has been used for studying the risk factors and the pupils’ school careers in primary education. Moreover, teachers’ beliefs about retention, learning and teaching have been investigated through a questionnaire administered to a representative sample of preschool and 1st grade teachers. The multilevel regression analyses show that the following variables are significantly predictive of retention in kindergarten: month of birth, gender, socioeconomic status, country of birth and at the school level, mean school social intake. Investigation about teachers’ belief shows that the vast majority of teachers are convinced that retention in kindergarten is beneficial for later achievement and not detrimental at a psychological level. Preschool and 1st grade teachers share some mutual expectations about the level of prerequisites for entering 1st grade. Even if they are no formal instructions or benchmarks, kids who are not “ready” should not enter 1st grade, but rather stay one more year in kindergarten. Those results can be related to the “culture” of the education system in Belgium, a non-comprehensive one: pupils with learning difficulties are kept apart from their age group or peers through grade retention, early tracking and special education.