I think he is at about the 4th or 5th grade level. Normally I would just order Saxon 54 homeschool kit (old edition) for him. Here's the wrinkle:
The prison limits each inmate to a total of ten books. If I have to buy a textbook plus an answer key plus a test booklet, that would presumably count as three books. Because I do not want to use up more than one book "slot," it is much better if I can buy something that has both questions and answers contained within the confines of a single book or workbook.
Also, the prison only accepts books fulfilled by Amazon.com.