At my school we have a hallway where I get 5th and 6th students to work with the mentally challenge. That's what we are here for. We know that kids think it's more fun, less memorizing, Students are much more accurate with numbers, their math grade goes way up, the students aren't stressed out, and they think they are smarter. If you do it right, they will be as fast as a calculator. This depends on the IQ or how hard the child wants to work.
Students learn a relationship with the numbers.
Teachers say that it is much easier to teach. Students have greater confidence. It is easy. First you teach the flash cards. Let them have the answer sheet tape on their desk.