The Mondrian cubes I did with 5th grade was one of those projects that had students working at all different paces so I ended up doing an extension with early finishers. Its just a simple as they look! They could draw anything they wanted and were encouraged to use a ruler to break up their drawing into squares and rectangles and color with primaries. Like most extensions many students took it another direction, but as long as they were engaged and creating with purpose I let it go!
You will see a few pumpkins/ghosts as this extension happened the week before and of Halloween :)