is it illegal to use copyrighted image for educational purposes?

[Madoka-chan]

Hi, I'm doing a project for AP English in which I have to present and teach my class about the forms of irony. My teacher encourages that we use visual as well, and while I have come up with my own visuals for certain examples of irony, I found an image on the net that I thought was a great example of situational irony. Would I have to have permission to use it? I'm not distributing or selling it; I just wanted to present the image to my class and explain how it is an example of situational irony. Of course I'll give credit to whoever made the image, but would I necessarily need his permission to use the image?

Thanks to anyone who can answer this. I'm afraid I'm not that knowledgeable of copyrighted laws.