We focus too much on the negative behavior in our classroom.
Even when I say, "I really appreciate how so and so is sitting," most of the time it's not for the purpose of complimenting that student, but getting a majority of the others to also sit.
We use too much sarcasm.
The 'good kids' - who are attentive and actually participate - get looked over.
If I were them I would start acting out just to get some damned attention.

Tomorrow that will change.
I will go to school armed with happy grams - blank note cards decorated with stickers and magic markers that will be put in kids' homework folders when they have a particularly good day, telling their parents something specific that their child excelled at that day.
I'm going to figure out how to modify and steal Amy's lottery idea to meet the needs of my students and I'm going to email professors for ideas of other ways to positively reinforce behavior that fosters more intrinsic motivation...
Something has got to break.
Most days I hate our classroom - they've got to, too.
I've got 5 weeks left to change that.