We recently had the opportunity to preview Time 4 Learning an on-line educational website for preschool ages through grade 8. It focuses on the subjects of Language Arts and Math, but also Science and Social Studies units as well. You can choose to set the timer for the lessons before a child is allowed to go to the "playground" to just play games. The playground consists of links to child safe places on the web including PBSkids.com.
The game-based learning offers a form of constant assessment. Games do not actively teach, they don’t say here is some knowledge for you to remember, but rather they provide constant challenges and then give you feedback on your decisions, and that is how you learn. One defining characteristic of games is that they evaluate the player. They accomplish this by giving explicit feedback or by using technology to modulate the challenges of the academic material and cognitive demands to sustain play and affect learning (Baker & Delacruz, 2007; Salen & Zimmerman, 2003; Schell, 2005). This description of games is almost synonymous with the notion of formative assessment. Games can provide a greater amount and better quality of formative feedback instead of weekly classroom quizzes, games provide constant feedback at the appropriate times in order to keep students in the learning zone. They also offer low pressure learning and encourage risk-taking and even failing.
I do recommend this site highly and only wish I had more time to explore the site. The site does cost a monthly fee $19.95 for the first child and $14.95 for each additional child. This can be a bit pricey for a larger family. The billing cycle begins on the day of registration and members are billed every 30 days. Members can start and stop at any time. Time4Learning has no hidden fees, requires no contracts and offers a 14-day money back guarantee. I say give it a shot and judge for yourself.