The idea behind this is that students progress in their abilities as they grow, maximizing the times that they are best able to receive information and using those times to set them up for success later on.
In a similar fashion, Montessori students use the "movable alphabet" to learn their letters and, eventually, learn to read. The movable letters allow children to hold letters in their hands and move them around to see how they look and how they can be combined to create words. The idea behind this is that students progress in their abilities as they grow, maximizing the times that they are best able to receive information and using those times to set them up for success later on.