Many state standards expect students to be fluent and flexible in their ability to compute numbers and require students to solve addition and subtraction problems using models. This resource includes 20 classroom-tested lessons that provide friendly, meaningful support for using ten-frames, one of the most important models teachers can use to help students anchor to the landmark number ten and develop all aspects of number sense. Three types of step-by-step lessons—routines, games, and problem-solving activities—provide students with opportunities to think, reason, and communicate about numbers. Teacher support materials include strategies for differentiating instruction; assessment rubrics; examples of student thinking; technology tips; teacher reflections; and reproducible ten-frames, ten-frame cards, and computation cards.