The author questions the necessity of synchronizing two transitions: from junior school age to adolescence and from primary to secondary school. The paper discusses new experimental data proving that transition to secondary school is a crisis and points out the necessity of designing a new stage in school education to ensure a smooth transition from primary to secondary school, a stage that is missing at present. An experimental analysis of academic achievements of more successful pupils allows the author to formulate a hypothesis as to how instruction should be organized in that transitional period.