"Math facts fluency leads to higher order mathematics. Through automaticity students free up their working memory and can devoted it to problem solving and learning new concepts and skills
Quite simply, a lack of fluency in basic math facts will significantly hinder a child's subsequent progress in problem-solving, algebra, and higher order math concepts. Math fact fluency not only affects our students' future success in math, but also in science and geography.
For these, and probably a zillion more, the Common Core Standards require us to insure that our students are fluent in their math facts.
Math fact automaticity affect performance in later elementary grades as students have longer and more complicated computations to complete. At this stage, if a student does not have his/her math facts committed to memory, he/she will spend a lot of time and energy figuring out smaller calculations and risk not having time (or energy) to complete the assignment.
Their performance in math class is not the only academic area that may be negatively affected. Other subjects such as science and geography may be hindered.
*(The above was borrowed from Peggy at Primary Flourish)