One way to learn about the Civil War for fourth grade is to include a Venn diagram lesson into your Civil War lesson plans. You can do this by comparing and contrasting the North and the South. Once you have completed your Venn diagram as a class (or students can fill them out individually), discuss the results and point out strengths and weaknesses of both sides. For example, on the South side, your students could write that slavery was legal. On the North side, you could write that the Union army was offering freedom to any slaves who signed up and fought against the South. Then talk with students about whether or not these issues were strengths or weaknesses for both sides. This discussion should lead to the reason why the North, or Union, won the war.