When we used the test out/compacting approach for math, the teacher used the school's curriculum for higher grades, using mostly independent work packets, with periodic checkins by the teacher. No need for designing individual curriculum. So our DC would essentially take a unit test every day until reaching one that was below the agreed on cut score (80% is a common one), at which point the teacher would hand DC a packet with that unit's work, give a brief run-down of the skills involved, and leave DC to work on it during the same math period as the rest of the class, checking in occasionally when other students were doing independent or partner work. In our case, this was successful enough that the teacher started doing it with other students who were scoring consistently in the upper 90s on unit tests. Slightly older primary grade class, though. For littles, I'd prefer some direct instruction, but if he's that far ahead, he may be able to get by with independent work for the time being--depending of course, on his executive functions.
