It should be noted that a child’s L2 competence cannot always be placed in a specific stage of ESLA; children sometimes display linguistic behaviours that are typical of different stages. Cummins (2000) states that it normally takes between 5 and 7 years of using and being immersed in a second language in order to acquire a level of L2 proficiency that is entirely suitable for schooling. 

The amount of time required to acquire this degree of L2 competence depends on a number of different factors, such as: 

• the age of first exposure to the L2 (generally the earlier, the better);
  
• the level of L1 competence;
  
• the quantity and quality of linguistic input in both L1 and L2 that the child is exposed to on a daily basis;
  
• the degree of motivation to learn the L2;
  
• the similarity and “compatibility” between the two languages;
  
• the child’s family’s Socio-Economic Status (SES). 
  

All these factors need to be taken into account by educators and teachers when evaluating the child’s L2 performance, in order to avoid mistaking errors that are typical of ESLA for signs indicating the presence of Specific Language Impairment or Specific Learning Disability.

Research has identified expressive vocabulary in L2 as one of the main weaknesses of bilingual children (Gibson et al., 2012), suggesting it should be one of the main targets of intervention programmes aimed at strengthening L2 skills. These kinds of intervention programmes are most effective when carried out at preschool or nursery level and when they involve explicit teaching of vocabulary and collaborative storytelling and reading (Barbieri & Bernabini, 2018).