I know school should be out, but our daughter has been rapidly advancing through the scenarios at Empire Earth, and it seemed like a good idea to have her learn the real historical context if she was going to be playing the Red Baron anyway.
We do see the educational potential of games like Empire Earth, but it is so complex and it takes so long to progress through the scenarios (even with cheats) that it's hard to know how it can be easily incorporated into the conventional classroom.
In our case, we see these historical SIMs as being useful memory pegs that kids can hang other facts or ideas on later. There's no doubt she has a better idea of the complex decision making of civilization building (including technology) and war, and she certain seems to retain the context and names of the events better than a film or book.
For any of you who might be interested, we've found these excellent links below. The lesson plans at the BBC site are helpful for making sure the kids have the main points and definitions, geography, and timeline. The BBC also has some animated games that require problem solving scenarios as well.
We'll planning to watch Sargeant York and read excerpts from his diary in American Courage.
World War One at BBC
BBC: History for Kids
PBS: The Great War
Blank Maps of Europe