Sigh. Our sopranos are ditzy too. But like you said, they usually get the melody, so it's not a problem most of the time. In my case it's the altos who seem to not have brains (this year, at least). I really don't understand - it's an audition-only choir, and one of the requirements to get in is decent sight-singing. And yet, we can't seem to read music at all. Every time our accompanist stops playing the parts, everyone except for maybe 2 or 3 of us forgets everything we just did. Even more pathetic is that we just started working on The Heavens Are Telling (from The Creation), which we sing every single year - and only about 3 of the altos are new - and we're still screwing up.

Good luck with your section practice. Even if I had enough room, which I don't, I would never have all of the altos over. I think I would kill them.