ElectroCity is an interesting online game designed for education. It's based around the SimsCity principle and users have to try to build a financially viable eco city where all the inhabitants can also be happy.
As I said the game was designed for education and there's a very handy teachers section with some downloadable worksheets. The producer put the level of the game at 7 - 9 year olds, but if you were using this with non English speakers for language development I think you could use it with any aga range and there would still be a good deal of motivation to try it.
There's also a downloadable version of the game for those with slower connections and wonder of wonders there is both a PC and a MAC version. It's quite a small download too ( 1 - 2 Mb). You can find these in the teachers' resources section.
You can also have a look at some of the cities other players have created.
If you register you can also enter your students in a competition to win a prize for the best designed city and students can keep track of how well there city is doing.
This looks like a really handy educational game.
Hope you enjoy it.