Onverse.com
Well for age 13 and up, there is no better free virtual world than Onverse!
the best game for a tween would be fantage its a cool virtual life get it its the best
girlsgogames.com I LOVE THAT WEBSITE
The best virtual world for tweens to play on is www.ourworld.com. it is easy to get started on and entirely FREE! On most virtual worlds you need to purchase a membership but on ourworld you don't. Most of the items are available for ALL members. www.ourworld.com is the best website for a tween virtual world.
Pop tropics is a good virtual world
Depending on taste: Free Realms or Club Penguin are the most popular I like stardoll but my fav is secertbuilders.com
If you are a kid or tween maybe Babydow.com.
poptropica
Usually, The "tween" age is 12 -14. By then you would have grown out of childish likes and begin growing up. The tween stage is when you are over 80. However, the asker is likely asking about the virtual reality game, not if there is a second part of tween life.
Probably the top ten virtual world games!SmallworldsBinweevilsclub penguinmoshi monstersWebkinzPandandamydinosStardollIMVUPoptropica
ONVERSE!it is the best virtual world sign up here
Neopets or fantage
LOL I'm a tween! Some websites I know are Fantage, Club penguin, moshi monsters, and not virtual but twitter!