Making a collage might be fun, but that's more of an arts and crafts thing. In a photography class, you learn about your camera and how to use it. You learn about proper exposure and how to achieve it. You learn about the elements of good composition, and how to apply them in your photography. You could also learn how to develop film and make prints in a darkroom. Then the instructor will critique your images, telling you what you did right and wrong, and how you can improve. You might also learn how to mount your pictures in preparation for framing them.
In a photography club, you get together with other like-minded people to discuss photography. You can present challenges to do for the next class, and hold photo contests. You can arrange photography field trips. You can do pretty much whatever you want that's related to photography. You can even make it a photo scrapbooking club if you want and do collages.
