I work at a primary school (year 6) age 10/11 and we certainly try to make them aware of all these words, homophones, as it makes a huge difference to their writing. I cannot tell you if English Language (grammar) is taught separately at secondary level. I still have difficulty accepting that now it is considered perfectly legitimate to start a sentence with 'because' something that in my old fashioned English Language lessons during the 1960's was considered inappropriate!!