I have received a telling off for using a word to reprimand a child for bad behaviour that they did not understand. The child thought I was calling them names. I was not. I have been told not to use words a child does not understand. I am at a loss as to how I should know in advance which words they might be. Is there anywhere any research with reading age and expected vocabulary? I thought conveying the meaning of new words was what I was meant to do, all the time. I have certainly reprimanded pupils in the past using far stronger language (not swearing or name calling, but certainly things like 'doing X is completely idiotic.' I know I need to think harder about what they might know, but my subject is by definition rather vocab intensive, so I do it instinctively. I teach 14-19.