Your best answer is for him to try an IELTS english practice test : http://www.ielts.org/test_takers_information/test_sample.aspx
If he feels comfortable, ask him to evaluate himself using the IELTS series of Books and CD's, with relatively less investment he should be in a position to assess which band he fits into. Like I said elsewhere you need not buy the books, I believe the local British council library should have the books available if you enroll as a library member.