You don't need to get a place for him before travelling. (It is students in universities and colleges, 18 or 19 years old or more, who have to have the offer of a place before they can get a visa.)

When you know where he will be living with you, you can Google "primary schools in (whatever district)", to find out what schools are nearby. (For instance, I just entered "primary schools in Waitakere", and this is what came up. https://www.google.co.uk/#q=primary+...s+in+waitakere) You can look at one of the sites that shows a general list, and then you can look at each school's own website to get an idea of what it is like. You can contact the principal to make an appointment to see the school and discuss everything.