Pairs of youngsters help each other practice estimating by playing a game of tic-tac-toe. Game sheets have level-appropriate math sentences in each box. (You need to create them: good news is they can be customized for your learners!) Players take turns estimating the answers and checking them on a calculator. Spend a little class time practicing this game and then use it as a partner game for fast finishers while you help individuals who need more attention.