Here's a great games based learing website to try out in your class - www.arcademicskillbuilders.com/

Without the need to sign up, your pupils can play against each other in fun maths, literacy and geography games. Simply head to the website, select the game you wish to play and create or join a game room for instant multiplayer quick fire questions.

A personal favourite is Penguin Jump - help your penguin jump to his homeland by selecting the icebergs with the correct answers.

BUT the website is American so please be aware if using the literacy or geography games.