John, I know you teach adults, and we are talking about how kids are different.
I happen to be in Bangkok at an Education Conference now so we are thinking about these issues!
The biggest effect on kids Education is the adults they encounter, parents and teachers and other mentors.
As great as I think Arduino is, I do not think the Educational material is there yet to just hand it to a kid and expect good stuff to happen.
I have lots of kids and lots more Grandchildren.. and I've tried lots of things... I have used Lego Mindstorms with kids and even with that well-researched educational system, kids often floundered around if left on their own..
The biggest factor is the adults kids interact with. Parents, Teachers, other mentors are the ones that involve kids with their own learning. So I am considering how to put together an Arduino offering for Parents, leading to learning by them AND their kids. I don't know how that will work, yet, but I've tried many things over 50+ years, and taught kids from 2nd grade to High School, and at University and IBM. And I don't know much, except that personal involvement by the students and they way they construct their own learning is what matters.
My kids learned a lot about electric circuits and switching with a few old IBM control panels that had a lot of switches and lights on them, a couple of batteries, and about 100 clip leads from Radio Shack. They built a Lunar Lander next to the furnace in the basement. 5 years later they were etching circuit boards in the kitchen. Today they are building systems with 3 Atmels in them, 10GHz chip receivers, doing BioChemistry at Yale, etc. I hope the difference was not knowledge per se, but a disposition to take things apart and put them together..
So, I wish I knew just how to help Parents and Kids do hands-on stuff together. I almost think that Parents should just start doing table top Arduino after Dinner, showing the kids what it's all about, asking kids what could be done with it, having them help.. and later 'allowing' them to do their own things. But never telling them they have "bought an Educational thing for you"
Let them find the receipts 20+ years later!!