These are some for any age:
Panfu
Fantage
These are just some of the ones I play. I dont really know any other fun ones for kids under 13.
Call of Duty Online
Bin weevils, fantage, secret builders, runesqape, world of warcraft, small worlds, our world
games online? i don't know what you mean but i think it can be club penguin, spineworld, farmtown, farmville, or cafe world. I don't know what you mean.
It is a good game for children k to 3rd grade
I got lods there is Bin weevils Clubpenguin Current local time in Canada (thats a REALY fun game) Current local time in U.K ( very good for kids) Our world (not that good LOL) secretBuilders and spine worlds
You can try Fantage (that is for kids, teens and older) Second Life( teens and older), or online worlds. com. Onlineworlds.com helps you find worlds. Good luck!
Well, Jumpstart is a very cool and safe online virtual worlds for kids 9 and up, as well as me, i play Jumpstart and it really really good for me!
Flight simulation, Air transporter, and Arm Surgery 2 are good online simulation games for kids. Sim taxi and The Sims are also great online simulation games.
Moshi monsters is an awesome game for kids who are 10. this is the link. moshimonsters.com
Neopets
Moshimonsters is an online pet game.
One can find a good review for kids online games on the games site themselves. Most online game websites for kids will have a section where you can read feedback about different games and sites. You can also use yahoo answers to look at some thoughts people have on different online kids games.