Yes it's totally worth it if you keep the nanny for years (through elementary school), then Junior High will probably enough to keep on practicing the language

Has anyone had a nanny speak another language with their infant/toddler? Did the child continue to speak the language later in life? We're considering having a spanish-speaking nanny speak only spanish to our young toddler, and to keep her through elementary school, but we won't be sending our DC to spanish-immersion elementary school or preschool. Is it worth it?