This series of lessons will prepare all students, particularly in KS2 and KS3 to develop their computational thinking skills, which is required for most KS4 qualification. It is also aimed at students aiming to sit GCSE computer science, and will support, provide a thorough and secure understanding of fundamental topics with adequate practise at applying skills. Decision making is an essential skills to master in computer science and students from any level can be guided through this lesson with teacher notes and make good progress. Starter plenary and homework activities included. This lesson is aimed at all abilities, although lower ability may require more time or lessons to complete all tasks. Lesson objectives are extracted from the new computing curriculum in England for KS2 and KS3. Although this lesson can be taught as stand alone, students who have already used algorithms in scratch series will benefit from continuity and familiarity of keywords and exercises. Students will need knowledge of how to use input and output function with knowledge of variables and lists in python. Alternatively purchase introduction to python - from scratch to python series. They will also need the python IDLE environment which is available to download free at https://www.python.org/downloads/release/python-350/. Please feel free to email email@example.com for feedback or further advice.