Research definitively proves that our minds are capable of distinguishing different languages from a very early age. Because students are only spoken to in Spanish from the very first day at Spanish World School, they very quickly know that they will hear something different at school than what they hear at home. And because we know that students receive an adequate amount of English outside of school (through conversations with friends and family, exposure to books and TV, etc.), there is no reason to believe that their English skills will be delayed whatsoever.