When I've been hard up for a quick and effective group project I have
the kids do a portrait of the principal or superintendant etc. by
dividing up a photo and having each kid do a value study of their piece
with ebony pencil. I find that the admin people are really tickled by
it and the kids can easily do it in a period or two. Make sure that the
best students get the eyes etc..
Anyway, if you have any ideas for a quick, 3-day, stunning group
project let me know!