Several researchers have drawn attention to the educational challenge posed by multilingual classes where students from different linguistic backgrounds coexist. Current institutional initiatives in Europe, but also elsewhere, advocate for the maintenance and promotion of multilingual and multicultural diversity within both monolingual and multilingual classrooms. In this study located in Spain, we were interested in exploring the English as a Foreign Language (EFL) vocabulary production and FL categorization of a group of heritage bilinguals in comparison with their mainstream monolingual peers. Results from a categorization task revealed that on most measures taken, heritage bilinguals, despite being a more heterogenous group, performed similarly in terms of vocabulary production in general, and as compared against the framework of a standard pre-B1 Cambridge vocabulary list, FL categorization, and typicality structures. The levelling effect of the EFL class is claimed to be accountable for this lack of differences. Furthermore, we dare speculate the generalization of CLIL could play in favour of more inclusive classes where immigrant learners are not left behind and can realise their potential to the fullest.