When my son began to have a difficult time in school last year I developed a behavior chart for my son (click here or go to "Printables" page) to encourage good behavior at school. We hung his chart on a wall. Every day that he did well in school he got a sticker to put on his chart (I found 180 motivational stickers at our local Dollar Tree). Each day he got a sticker he got a privilege of his choosing (30 min. of video/computer games, extra time outside, etc). After he earned a certain number of stickers he was given a reward (toy, book, special time with a parent, etc).
I also created a behavior chart for the teacher (click here) to fill in and send home each day. I added clipart of cartoon characters that my son liked to personalize it. This chart helped made sure the teacher, my husband and I were all on the same page when it came to keeping my son on track at school and at home. These charts really helped us and I hope they will help you too!