(From a comment to A Better Way to Teach Math:)
Jump Math has profound implications for education. I myself was a child who excelled on all aptitude tests, fulfilled that promise in the liberal arts, and began failing miserably in math in 5th grade. I had so many teachers whose approach to teaching math was to go to the board, scribble scribble scribble, covering the board with numbers and squiggles and symbols, and the things they were saying made as much sense as "so you take the giraffe and turn it upside down like this, and then the elevator stops, and you torque the red balloon this way, and reverse the mayonaise, and...there!" The teacher would turn around with a big smile and say, "So! Did you get it?" "No, I didn't "get it"!!!" I wanted to scream, "You didn't explain anything!"
This was how math got taught badly the traditional way.