Rationale: Students build fluency and automaticity of basic facts.
CCSS: 2.OA.B.2 Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers. See standard 1.OA.6 for list of mental strategies.
3.OA.C.7 Fluently multiply and divide within 100, using strategies such as the relationship between multiplication and division or properties of operations. By the end of Grade 3, know from memory all products of two one-digit numbers.
Other grade levels this could work for:
Grade 1 – Grade 6