Celestia is a space simulator that lets you travel in our universe. You can explore the entire solar system and even go beyond our galaxy. Celestia doesn't just show you the sky, it lets you view the universe from any point you want. If you are familiar with Google Earth, it will be easy to use the program.
You can capture images and record videos, so you can use the program for your school projects. The program is also useful to learn information about planets, satellites and stars.
If Google Earth has Sketchup and 3D Warehouse, Celestia has Motherlode, a repository for 3D models and textures.
Celestia is open-source and it runs on Windows, Mac and Linux. After running the program for the first time, go to Help / Run Demo and select the full-screen mode.