Persuasive writing has cross-over with so many subjects and is a very useful element of English to learn for all potential career paths (see this worksheet example). It is also something that scientists and mathematicians need to master in order to convincingly present their findings. The world of business of course also requires strong communication skills and jobs like marketing, PR and sales all involve persuasive writing.
You can support your child to develop these persuasive writing techniques by encouraging them to use writing to express things they feel strongly about. Capture all the energy they put into nagging you for something by asking them to write up their case for your consideration – who would have thought a request for a new game or gadget could be so educational?