If you're in PA, other than in Philadelphia (where the age is six), compulsory education begins at age eight, so you have until third grade to homeschool without reporting or complying with any requirements.
http://www.education.state.pa.us/portal/server.pt/community/overview_of_homeschooling/20312And I would second Singapore Math. If he's already on beginning multiplication and multi-digit addition/subtraction, you might consider using their placement tests (singaporemath.com), as, though clearly he won't need to begin from the beginning, there may be topics that have been covered in a different sequence than the books you've already used. His method of adding from the left, btw, is one of the methods taught by SM. I loved the mental math parts, as well as the problem solving.
