The apparent optionality in the use of null and overt pronominal subjects and the apparently free word order or distribution of preverbal and postverbal subjects in Spanish obey a number of discourse-pragmatic constraints which play an important role in Spanish L2 subject development. Although research on subject properties at the syntax-discourse interface has been conducted in adult L2A and bilingual L1A, child L2A has not been extensively explored in this respect. This paper explores the L2 development of syntactic and discourse properties of subjects by British child L2 learners of Spanish in the context of a Spanish immersion school and in three different age groups, namely five-, ten- and seventeen-year-old children whose age of first exposure was at four years old, and in three corresponding control groups. Research is carried out by means of grammaticality and preference judgment experimental tasks and results suggest that children can indeed acquire the syntactic properties of Spanish subjects, although not fully in the case of the first two age groups, while the acquisition of discourse properties seems to be delayed and remains problematic even for the older/more advanced group, as has been suggested for adult L2 learners.