Addition and Subtraction to 20
Addition and subtraction to 20 is the computational core of Grade 1. The BC curriculum emphasises understanding of operation and process, not just answer-getting. Students learn three key strategies: counting on, making 10, and using doubles. Number talks are the primary instructional vehicle: short whole-class discussions where students share mental strategies for a single problem and learn from each other.
Three key strategies
Counting on: start from the larger number (8+3 becomes 8...9,10,11). Making 10: bridge through 10 using partner facts (7+5 = 7+3+2 = 10+2 = 12). Doubles and near-doubles: 6+6=12, so 6+7=13. These three strategies cover virtually all Grade 1 addition facts. Students who know all three are computationally flexible.
Addition and subtraction are related
13-5=8 because 8+5=13. One fact gives four: 8+5=13, 5+8=13, 13-8=5, 13-5=8. Fact families make this inverse relationship visible. Students who understand it have four times as many facts available compared to students who treat addition and subtraction as unrelated operations.
Number talks build mathematical community
A number talk: pose one problem, students solve mentally, share strategies, teacher records without judgment. Tell me more. Did anyone think about it differently? How are these strategies similar? Over time, students internalize each other's strategies. The talk is where mathematical reasoning becomes visible and social.