Changes to school curriculums increasingly require the introduction of computer science concepts to younger children. This practical report compares three existing tools for teaching computer science concepts: unplugged computing, tangible computing and MIT's Scratch. We specifically focus on the use of these tools for school pupils aged 5--7. We describe a comparative study with 28 pupils from three rural UK primary schools that explores engagement with, and effectiveness of, each tool. As far as we are aware this is the first such comparative study of its kind. We demonstrate that the studied tools can be used to successfully introduce core computer science concepts to pupils as young as 5 years of age, that the methods used by teachers to deliver computing curriculums may greatly impact the learning outcomes, and that particular care needs to be taken to ensure that pupils focus on learning concepts rather than learning tools.