I was taught to uses only Crayola crayons on fabric, but do not use the washable crayons, just regular ones. You can cut the blocks and iron on freezer paper on the back to stabilize the fabric so it can be colored on. Use a fabric marking pen and draw a line about a half inch inside the edge of the block and tell the kids not to draw between the line and the edge of the fabric. After they have colored their block, tear off the freezer paper and lay a paper towel on the ironing board. Place the colored block face up and then place another paper towel on top. With low heat on your iron, gently press the blocks to heat set the crayon into the fabric. Do not slide the iron across the block, just press and lift and press again until the crayon is set in the fabric. This makes the blocks washable. You can trim the blocks into the same size squares and use a sashing to put them together. The kids will love to see how they worked together to make a quilt. I have heard of some classes doing this and then having a drawing on the last day of school for the winner of the class quilt. I have also heard of the kids raffling the quilt for charity. The ideas are endless. I hope this helps.