Learning a new language and a new culture

My son entered kindergarten this year.  He is attending a Mandarin immersion program at school, which means he is taught basic subjects (math, history, science, art, culture, etc) in Chinese for 80% of the day, and he learns English (reading, writing, speaking) for 20% of the day.  It has been one month since he started and already he is speaking and thinking in Chinese.  He comes home every day with a new word that he has learned. Lately it is a whole set of words.  He can say "Hello, my name is Texas and I am 5 years old." It is amazing that he picks it up so quickly.