Despite contrary research findings, many lay people still claim that starting second language (L2) instruction early yields linguistic advantages. This assertion is again undermined by a five-year longitudinal study conducted in Switzerland testing English language skills of 636 secondary-school students, who had all learned Standard German and French at primary school, but only half of whom had had English from age 8, the remainder having started English five years later. The results suggest that age-related attainment effects are overshadowed by other effects, yielding diverse outcomes according to individual differences, and contextual effects mediating L2 outcomes. An earlier age of onset (AO) proved beneficial only for children reared as biliterate simultaneous bilinguals receiving substantial parental support, as opposed to monolinguals and non-biliterate bilinguals (simultaneous or sequential); these latter failed to profit from their earlier AO. These issues require studies which explore what underlies SLA age effects and investigate how learning contexts shape processes of L2 development.