Assess students' ability to solve addition and subtraction word problems within 20 by modeling and computing with number lines and manipulatives; tasks require selecting an appropriate strategy (counting on/back, making ten, using groups), representing the problem on a number line or with physical/pictorial manipulatives, writing the matching equation (including missing-addend items), and explaining reasoning; include one- and simple two-step problems appropriate for Pre-K–Grade 2.