Here's a series of 7 lessons by LearnZillion on writing an argumentative essay. It is suitable for middle school students. It takes you through a step by step process writing approach to writing an argumentative essay.
Crafting an argumentative essay involves the process of brainstorming, planning, drafting, revising, and editing.
Topic: Water as a precious resource and the impact of not saving water right now.
8th Grade Argumentative Writing