Have him sit down for like an hour a day with Khan Academy. Then there are many other places he can pick up and practice math and other subjects if he gets through those.
I have a Filipino kid who works for me in a small LLC that I own. He moved here to the US with his family about our years ago after graduating from school in the Philippines. He is trying to join the military and having a hard time with the ASVAB test. Some of the questions he told me that he is having problems with are basic math problems. One of these is to calculate the area of a triangle. I had to think about this one because it has been a while. (Height * Base *1/2 in case anyone else is scratching their head thinking about this one). I also asked him what 1+2*3=. When he told me 9 I asked him if he knew what the order of operations were he said "no". I explained to him that the order of operations were brackets (), then multiplication and division (left to right), followed by addition and subtraction (left to right). Due to the order of operations this means that the answer is 7. He then told me that he really liked working for me because he learns something every day he comes to work, and that he was never taught the order of operations in school.
This makes me hope that the extra two years added to the school curriculum in the Philippines will be used to educate the students.