We coordinate our movements according to our internal body map. At some point in our lives we make up our minds where the legs ends and the back starts, which part we consider neck, and so on. A lot of people have only a faint idea where their hip-joints connects the legs to the pelvis, and so happily bend their spines when asked to lean forward from their hips.
Most schools don't teach anything to increase body awareness, or to understand the body dynamics involved in movement. Depending on the type and amount of physical activities, and the good or bad examples given, our body map gets more or less distorted. We can re-align our body maps by experiencing the location of our joints, bones, muscles and other tissues. The more we incorporate the experience of the connections of our structure into the internal body map, the easier movement will be.