Not unexpected, those who are bilingual experience a switching (one of the best known executive functions) advantage, but this was not the case for other EFs such as inhibition, attention, monitoring, working memory, and planning.
The hypothesis that bilingual children have a cognitive advantage related to their executive function has been accepted as a truth in both society and research. However, the present meta-analysis, which is based on a large number of studies (143 comparisons and 583 effect sizes), gives little compelling support for the position that a bilingual advantage exists for overall executive function. Importantly, there was large heterogeneity in results and studies of middle-class children and studies using switching tasks, and studies from one lab demonstrated larger effects.
Bron: The relationship of bilingualism and cognitive advantage
Original article: Is Bilingualism Related to a Cognitive Advantage in Children? A Systematic Review and Meta-Analysis