Recent investigations with young learners have proposed form-focused instruction (FFI) interventions as a way to expand their attention to problematic grammar features. A call for research on the benefits of FFI for both language use and language development, as well as for further investigations on the interface between FFI and language-analytic ability has been made. To fill this gap, this chapter compares the scores obtained in a grammaticality judgement task (GJT) by 33 Basque/Spanish bilinguals aged 10, divided into a dictogloss + self-correction and a dictogloss + metalinguistic explanations (ME) group. A correlation analysis is also conducted between their GJT scores and their language-analytic ability. The gains obtained by the dictogloss + ME group are in line with previous research examining knowledge of possessive determiners in the case of adolescent learners in both Canadian immersion programmes and other limited-input settings, confirming the effectiveness of ME. The marginally significant association between the dictogloss task and the GJT found in the dictogloss + self-correction group seems to support the contribution of the accumulated experience during hypothesis testing while reconstructing texts to metalinguistic knowledge over time. Additionally, the results suggest a levelling-out of participants’ language-analytic ability thanks to FFI interventions.