Michael Schoch, Answers questions on Noodle
I called Holy Family Elementary School and learned that it does in fact accept international students and has recently accepted several new students from China and elsewhere. However, international students must get their own visas. You can read about the school's tuition costs, as well as its policies and upcoming events on its website.
Since I don't know who your nephew will live with, or if you are a resident of New Jersey, where the school is located, I recommend that you call Holy Family Elementary directly at (973) 377-4181 for more specific information.
Best of luck! If this school ends up not meeting your needs you can search for other elementary schools in New Jersey on the Noodle School Locator.