Start with what they already believe
Traditional persuasive writing teaches structure: introduction, three points, conclusion. Students write about why the school canteen should sell healthier food. Boring, generic, no real conviction.
Better: Start with something they genuinely want to argue for. Should their local footy club be funded by the council? Why should their mate believe that anime is better than superhero films? What's one rule they'd change at school, and why?
Real persuasion comes from real passion. When you tap that, the writing improves without you having to drill it.