Abandonware Educational games
Educational game is all about helping children to learn their school program. Some will teach history, other will do mathematics or even creativity through creation of an illustrated story. A good educational game gives enough fun to the player and allow the lesson to be easily learned.
In the Educational genre, you may want to play 1893: A World's Fair Mystery, 3D Hypermaths, A.J.'s World of Discovery, Add It!, Addition-Master. Those are just suggestions, you are welcome to download any game!