It looks like this project is aimed at the younger child, but I think older children may enjoy it as well.
Fun project. Supply kids with magazine image, they have to draw their hand holding the image and imagine a background.
Paper value landscapes - 10 min project for older kids. Darkest up front, lighter as progress back.
Warm and Cool color project with value- reverse colors and use with Chromadepth glasses- physics of light and color-
Paintbrush Rocket: Ton Schulten 3rd Grade Cityscapes
Landscapes in tonal gradation, I would have each student do the same type of landscape for simplicity (city or mountains)
Bearden inspired cityscapes (art teacher's blog - neat!)
Making reflective print cityscapes. [Could be used for making reflective landscapes.]
3-D sky line: I love this! You can use recycled materials. I see this for 5th grade
City Prints - could do a Hundertwasser version with inked background and fold the paper down the centre while the ink is still wet to create the reflection.