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A study by the Henry J. Kaiser Family Foundation in 2005 found that kids spend an average of almost an hour a day playing video games. I'd say that's definitely true in my family. My kids get up before the alarm goes off in the morning to get in about 20 minutes of gaming, and then spend anywhere from 30 minutes (by themselves) to an hour (with a grownup playing with them) gaming in the afternoon.
I don't think my kids are unusual. They play Wii and love Club Penguin on the computer and other similar games. From talking to other parents, I think my kids are about dead on in their gaming habits (compared to other New Yorkers, at least).
Which leads me to think that if they're spending time gaming anyway, why not shove a little learnin' in their heads while they're doing it? The DreamBox math games are real actual games, not just worksheets with animation, so kids who play the story games (like Club Penguin) will love them. And not realize they're learning skills that will make school easier in the fall.