"Reward is most effective when it is contingent on the attainment of some standard of performance" (Classroom Instruction That Works, p.55).
"The research indicates, however, that the most abstract and symbolic forms of reward are, the more powerful they are" (Classroom Instruction That Works, p.57).
"[V]erbal reward seems to work no matter how one measures intrinsic motivation. Tangible rewards, on the other hand, do not seem to work well as motivators, regardless of how motivation is measured" (Classroom Instruction That Works, p.57).
"[T]hese tokens [stickers, coupons, treats] do not necessarily diminish the intrinsic motivation if the tokens are given for accomplishing specific performance goals" (Classroom Instruction That Works, p.59).
Even in the best of years, I have to change up my consequences and rewards frequently. They just stop working. Ultimately, I think a teacher would need to individualize the reward system--that would give it teeth. My assistant principal speaks of "currency." I understand that, but I have no confidence in myself to determine the currency of every student. For me, I want to focus on strengthening faith in effort, offering frequent, positive, verbal feedback, and a simple token system that I have in mind. I'll share that system later--I'm still working on it.