I think my DS8 would like the Life of Fred books but I'm confused where to start the series. He has little tolerance for "boring" stuff that he already knows so if I start him too early I risk turning him off from the series all together. Any advice?

I'm really not sure exactly where he is with math. His winter MAP was 237 which is was the top 99+% nationally and top 98% for our high performing district. He's in 3rd grade but is in pull-out math which is a one grade level skip so he's doing 4th grade math in school. It was a long hard fight to get him into the pull-out so there is little hope of getting the school to do more even though he still complains that he isn't learning anything.