At the beginning of the year, I give each student a laminated sheet of light-coloured construction paper and an eraseable pen. When we have, for example, a math lesson, I have my students follow along with equations on the board. They copy the equation down on their laminated sheets. When each student has solved the equation, he/she raises the sheet in the air. This way I can easily see who has the right steps and answer and who doesn't, thus making sure that those who have it wrong keep trying until I see they have the right answer. And the fact that the sheet is eraseable means less paper waste in the classroom!