10 year olds
There are images all around the walls of the art space. The children chose one to make a pencil sketch of. I encouraged as much detail and shade as they could include. This is so they will have options later. I asked them to 'zoom in' on their image, cropping off unwanted parts, focusing on the parts they liked the best. This is the part of the image that they will draw on their large coloured pastel paper (paper that has quite a rough surface, to capture the chalk dust).
They used a black wax crayon to draw their image.
Once they had drawn strong lines, they coloured it using ordinary blackboard coloured chalk. I asked them to blend every colour they used with another colour, so the change in colour couldn't be seen.
They went over the crayon lines with a dry paint brush to remove as much chalk dust as possible. They then put a line of black P.V.A. over the crayon lines. This could be done first, before chalking, but it takes half a day to dry depending how heavy handed the kids are.