Awesome post. I have my own lessons stacked up because for the last couple of weeks i've just been using yours. I did the world lesson last week and it would be stupid not to follow it up with the space lesson.
May be this is just me but I think it's a bit harsh using ppt's from the high school section on middle school students. For me, I don't care as I'm leaving in september but it'd be awkward setting up to teach a high school lesson next year and kids saying.. "teacher, last year, last year".
Anyway just a thought. And I can understand middle school teachers not wanting to miss out on this awesome material.