Weddingbee boards

For 6th graders, I would also try to mix it up.  Don't just have them do one activity all period.  So you might want to do 10 minutes of introduction/guided note taking, then something more interactive where they can work with partners for 20 minutes, then something else to bring it all back together as a class for 20 minutes (assuming you have 50 minute periods). 

Also, the biggest thing I learned when getting my teaching cert. was to make sure you have clear goals and that all your activities somehow contribute to reaching those goals.  So instead of "Students will learn about the renaissance" have something like "students will learn identify 4 major artists from the renaissance and explain the contributions of each."  And keep your lesson tightly focused on your goal.  So, for example, while it might be interesting to mention all of DaVinci's inventions or talk about why the teen age mutant ninja turtles are named after these artists, don't let yourself get drawn down those rabbit holes too far.  Always bring it back to what your goal is, and be able to articulate to your observers why your goal is important, and how each and every activity contributes to accomplishing that goal.

Also, it is nice to have a "ok, what have we learned today?" moment at the end of the class to quiz the kids a bit, make sure they understood what you were getting at, and to have a chance to restate the main point for any stragglers.  Try to find ways to assess whether all the kids are keeping up too.  The kids who get it will be the ones who volunteer, and you don't really have to worry about them.  But if you have an opportunity, like say during group work, go around and check that the quiet kids are getting it too.

Good luck, and what a great opportunity!

I think since it is a teaching demo, it is important that you actually teach a lesson and not just give them instructions for an activity and let them go to town. Greenleaf has some great ideas. And I think class participation is key.