Hi,, To stop this prize game,, which really looks like a magic part of teaching at the very beginning,, turns into a big disaster just after few days.. my suggestion to you is as follows,, tell your students that they are decision makers,, and you want their openion to have new ideas to praise them,, let them tell you the best things they mostly like to have or do,, while they are brainstormung, you come up with your suggestions as if you are offering help to them,, such as: what about stickers for Spongebob? or winning the class cup (a prize from the school for the best class, you might suggest to the admin. to start it) or giving a big star to the whole class, or start choosing (student of the week),,( student of the month) and on..
I hope this will work,,
thanks
WBT teacher..