It is not a one-sided curriculum. They also require lessons and activities based on the imagination and as well works produced from remembered experiences. That's okay, I can't read and write either. We need to realize that, like other skills, if the skill of observation is not taught, only a few discover how to learn it on their own. Using viewfinders and other obervation practice techniques, any teacher can help children learn to draw any object, person, animal, and so on.
Children can begin practicing observation drawing beginning in grade one and younger.
This is not to say observational drawing needs to replace their drawing from memory and imagination. However, if young children are not helped with observational drawing, many children mistakenly grow up believing they can't draw because they lack talent. It is true that they lack ability, and because no teacher ever helped them develop, they generally end up without talent. Talent needs nurture in order to flower. If they do not have observational drawing practice when they are young, most children at about third grade realize the inadequacy of their childlike images.