This is the third activity in the bundle created for CS Education week, for the Hour of Code, but can be used for a computing activity throughout the year.
Students as young as Year 3 (7-year olds) can be given this to work on (and maybe younger!)
In this activity, students are introduced to the idea of an algorithm. They are shown how you might draw a key for an image and are then asked to write out the algorithms of various images. Solution given for first image.
Additional grids are given for students to create their own images and algorithms. Perhaps they can give their algorithm to a peer to see whether they can create the image.
A spreadsheet version of this activity is also available.
Additional links are also given at the bottom of page 5 for them to venture onto other computing-related tasks.