I tried out the DR kit for awhile with my dd. We had already been using CM methods in our reading lessons (learning words in context, doing word building exercises as we encountered new sounds/word families/phongrams), and I would say at that point she was already reading on a similar to level to what you describe your son as doing. I tried it because I liked the idea of the lessons being laid out for me since I was doing my own thing at the time (no kit available when we started). While I liked it in theory, we ended up dropping it because I wanted to be able to customize to my dd’s reading ability and concentrate on the sounds/words that SHE needed to work on, rather just what the teacher’s manual said. I felt like we were spending too much time on what we already knew and not enough on what she still needed work on. Perhaps it would have been different if we had started with DR from the beginning, but since we didn’t I found it didn’t suit our needs at the time. Instead, we went back to what we had been doing – I had her read to me daily out of one of the Pathway Readers or another book of her choice, and we addressed new sounds/rules/patterns through word building (with letter tiles, as CM describes) as they came up.
HTH some,
Jen