Omission of Key Stages 

I came to this article looking for an explanation of Key Stages. As they are central to how most schools in England work, rather shocked to find they're not even mentioned. Sorry, but I do not have enough knowledge to add this myself, but I will add something that links to the 'Key Stage' wiki page. As well as understanding the Key Stages themselves (meaning of grades in particular, grades we get sent on school reports such as 6a bear no relation to my own schooling experience), what I was looking for is how they work as my son is at a school that completes Key Stage 3 at the end of Year 8 for 3 subjects, and at the end of Year 9 for all other subjects. The 'Key Stage' wiki page also lacks any explanation of the grades used.