In this study we investigated 107 young learners’ L2 English receptive vocabulary knowledge and speaking skills at two points in time, before and after the onset of instruction. We also investigated the role of several individual difference variables: out-of-school exposure to English, length of instruction, analytic reasoning ability, working memory, L1 vocabulary knowledge and prior L2 knowledge. Results show that L2 English proficiency in receptive vocabulary knowledge and speaking skills greatly improved over time and that the effects of schooling and contextual learning are largely additive. The main predictor of the children's proficiency at time 2 was their L2 prior knowledge, which they had acquired through contextual language learning before getting formal education. When considering the other variables that predicted L2 proficiency, the contribution of internal variables (L1 vocabulary size and working memory) was considerably smaller than that of external variables (out-of-school exposure and length of instruction).

In this study we examined the level of English proficiency children can obtain through out-of-school exposure in informal contexts prior to English classroom instruction. The second aim was to determine the input types that fuel children's informal language acquisition. Language learning was investigated in 780 Dutch-speaking children (aged 10–12), who were tested on their English receptive vocabulary knowledge, listening, speaking, reading and writing skills. Information about learner characteristics and out-of-school English exposure was gathered using questionnaires. The results show large language gains for a substantial number of children but also considerable individual differences. The most beneficial types of input were gaming, use of social media and speaking. These input types are interactive and multimodal and they involve language production. We also found that the various language tests largely measure the same proficiency component.