My goal is to get them very comfortable in abstraction and color because I find that if you start with realism first, you can potentially have artists who think about color, shape, and relationships between those things as secondary, if they think about them at all.
For my sons kindergarten class we looked at Jasper Johns' 0-9 series. JJ drew the numbers 0-9 right on top of each other, so that the final result was a bunch of shapes, and the numbers became secondary. Then he addressed the resulting shapes with color. This seemed exactly the kind of thing that kindergarteners could tackle, and feel confident.
I also like that this project addresses many things that kindergarteners are learning about - writing numbers for example. Shapes, colors. It's all very curriculum appropriate.
Jasper Johns, 0-9 Series