Too, you have to realize that MOST people send their kids to school when they're supposed to go to school and don't think too much about curriculum appropriateness and whether their child is being challenged enough. They don't have to. School does tend to operate well for the majority of kids. So, your husband may not know any others of his parent friends that give much thought to the whole school thing. We have lots of friends whose kids are plenty smart, but they just feel content. And, admit it, it CAN be hard to go against the grain and do a little rabblerousing to get what we need for our kids. Maybe your husband just isn't used to much rabblerousing!
Funnily enough, even though I knew our kids were gifted and needed some accelerations, I'm the one in the family who doesn't like to make waves. My DH was always saying to "just tell them that they need to do it!" I was much more worried about rubbing people the wrong way and more concerned about being polite throughout the process. So, obviously I don't know your DH, but maybe he agrees with the need but is just more laid back in his approach.
On the other hand, I feel the need to read everything I can get my hands on so that I feel prepared to defend against any challenge anyone may bring up. My DH, though, is confident enough in his own assessments that he feels no need to read about all the specifics. Truth be told, I AM the one who ends up in conversations with people about school, just by virtue of the fact that moms talk amongst themselves a bit more than dads do. So, I do have to have well-researched thoughts on the issues and my DH just does not.