Following the Common Core Standards in Math, 2nd grade students should be fluent in their addition and subtraction facts up to 20. I put a stopwatch on the board and give each student their test. When they finish they write their name on the bottom of the page and their time. If they pass they get to go on to the next fact, otherwise they keep trying until they are under 3 minutes and all correct. Check out my Math Pizza Incentive for passing all their facts and be sure to check out my subtraction facts tests.