Our carnival is in the fall usually right before Halloween. We use candy as prizes. Amount or type of candy is determined by the teacher running the booth. Some charge 1 ticket (25 cents) and you only get one piece of candy. Or they may charge 2 tickets and you get a candy bar. It really varies but the kids love the candy. Since it is around Halloween the parents don't seem to mind. Last fall our carnival earned the highest ever. We even changed our cake walk to a junk food walk because of the home-made items at school health code(it doubled it's earnings).
I read in one of the threads (can't remember which now) that one school's carnival had less attendance subsequent years because the first year they did it the prizes were cheep. The parents weren't as interested in returning.
Maybe I like the cheesy stuff and don't know it. Someone clue me in. We may be doing a carnival soon and as they say "If you're gonna do it, do it right."