Step 1: Materials
* Solid colored t-shirts
* Cardboard, plexi glass, or chip board. A strong surface for working on that won't allow the bleach to bleed through the fabric to the other side.
* Chalkboard chalk
Step 2: Sketch Time!
Take your piece of chalk. If you only have one break it in half. Sharing doesn't come naturally to kids, so make sure there's enough chalk for everyone! All they have to do is sketch their design onto the shirt with their chalk. Its not as easy as it looks to draw on fabric, so reassure them that mistakes are ok, the chalk will brush off and you'll only put the bleach where its supposed to go.
Kids art is never what you envision. My son, who is four, told me he was going to draw a dragon on his shirt. He made line after line, paused to study his work, then looked at me and said, "its a machine!" OOOOooookkkaaayy! Gotta love it.