The trick is very simple!  Each card has the numbers from 0-15 on them. 
Ask a volunteer to choose a number between 1-15.
Go through each of your teacher cards asking, "Is it on this card?"
If the number is on the card, you look at the number in the middle of the card and put that in your head.  All the cards that he says yes to...you add up the middle numbers and that is the number he/she has chosen.

I give the students the handout to practice the numbers and the english trick then I hand them the number cards and some thick paper to make their own number sets.

I've not done this with a full class...only with my extras.  It was very simple, very fun and we all enjoyed it!

Sonya

Thanks Meke!  I like this one too...I like to use magic in the classroom and will teach the odd trick...not too many though to elementary...many of them are a little upset that it's a trick and not really magic!