Here I look at how fluency is best thought of as ‘multi-stage cognitive processing speed’. Note the emphasis on the individual being guided to attain their optimum processing speed; we are all different, but we can all improve our number knowledge ability in respect of individual potential. Worksheets and textbooks have a time and a place, but can be used incorrectly for number knowledge, since they lower the expectation of thought-speed and open the door to inefficient strategies being used, potentially actually harming gains made in face to face teaching.