What factors contribute to the proficiency of young EFL learners in primary school? Assessing the role of CLIL intensity, extramural English, non-verbal intelligence and socioeconomic status

Although multiple factors influence language proficiency in instructed settings, the prevalence of content and language integrated learning (CLIL) research in recent decades has placed intensity of exposure (via CLIL lessons) at center stage, sidelining other variables. This study aims to rectify this by examining the impact of CLIL alongside three additional factors: extramural English (EE), socioeconomic status (SES), and non-verbal intelligence (NVI). Specifically, this study analyses the interplay of these variables in the proficiency of 171 young English learners (aged 10–11 years) in Navarre, Spain. The participants were divided into a low-intensity (LI) ( n = 54) group and a high-intensity (HI) ( n = 117) group depending on exposure to English in school. Results indicate that HI learners are superior in reading, and even more clearly in speaking. EE is very frequent in both groups but more abundant among HI learners, and it shows several positive associations with learners’ scores. Higher NVI levels positively correlate with all skills in both groups, except for speaking, which appears to be affected by EE and, to a lesser extent, by SES.