Hi Bryce,
Some time ago I did camera and compositing for a music video.
You can see it here:
http://adeszo.nl/articles/428
Is this similar to what you want to achieve? If so I'll explain the workflow.
First we shot a clean plate of the classroom without the artist. This shot was used as the background.
Then we had him with different outfits sitting on different chairs in the classroom with a collapsible greenscreen behind him.
In post I started on the layers where the artist was sitting in the back row. Then I made a garbage matte around each shot and I keyed out the greenscreen. I worked my way up through the layers and the topmost layer was the solo of the artist as he was standing in front of the classroom.
The camera was locked off for all the shots ofcourse.
I hope this can be of any help.
Kind regards,
Robbert-Jan van der Does
lighting cameraman/steadicam operator/editor
WISIWYG (What I See Is What You Get)