In this lesson, your students will be shown arguments for both sides of the debate - in a depression, should the government spend more or less? Classical economics says that government should get out of the way - with reduced taxes and less bureaucracy, private industry will fix the slowdown. Keynes said the exact opposite - by injecting money into the economy and hiring people, you could stimulate demand and fix the slowdown.
This is a very difficult lesson involving higher level economics concepts. Your students will receive a worksheet with four simplified arguments for each side and are asked, "do you buy this?" Even though it is difficult, I think it is essential to introduce students to the debate between classical and Keynesian economics as it essentially will shape who your students will vote for in the future - better to tell them about the subject now so they begin thinking about it.