Coding is designed for all primary age pupils as it builds on one another. But is can also be useful as an introduction to coding and the basics of HTML and python for Key stage 3 pupils. Pupils do not have to start with Block Coding as a language. The content is not locked because Discovery Education encourages exploration according to skill and interest.
In the lesson plans, Discovery Education has provided some scaffolding for how the content aligns to the National Curriculum. You will find that Block ranges from KS1 in the first lessons up to KS2, Python and HTML are aimed at UKS2 and KS3 For no coding experience, Block is always a great place to start, even if older than Primary age pupils.