Hi! I hope you'll love Colorado, we certainly do! There is a lot of changes going on with education. The whole state experienced budget reductions, but I think most counties are clever enough to figure things out so that quality is not compromised. As others mentioned, Douglas county just went from track to traditional. I'll actually miss the tracks! I think Colorado in general does a good job, but you really can't go wrong in Jeffco or Douglas, and others mentioned Cherry Creek- which is as good as Douglas.
We personally moved here and chose Douglas county, as an educational psychologist I found it to be the better choice for us. And I'm thrilled with our choice. But really, if you are an involved parent (which you obviously are, doing all this research), you will be able to advocate for your kids and do just great.
If you choose Jefferson county, Normandy elementary has an EXCELLENT program for learning differences. Someone mentioned that dyslexia is not a recognized factor, I've never heard that. But even if that's true, the schools are great and he will get the help he needs. Good luck!