Through the peaks and alleys of my journey I developed a teaching philosophy that is mutually dependent upon a Curriculum and an Environment. In order to have a productive learning session, I need to consider the particular needs and abilities of all of the possible learners in the session, have a plan that allows for each possible combination of these needs and abilities across physical, social, psychological, and emotional ranges to be accommodated and engaged in such a way that fosters growth and leaves the learners at the end of the session satisfied with their individual and collective progress and excited and confident of future progress. The field of developmental psychology, particularly in light of Cognition Theory, allows one to identify what those disparate needs and abilities might be. The keys to doing this are having a well developed, progressive, age-appropriate, flexible curriculum administered in a safe, engaging, flexible environment and founded upon a psychological understanding of the intended recipients. The good news is that the human brain is the most powerful problem solving and information processing engine in the world, so if you do provide a well developed curriculum and a healthy environment appropriate to your audience you don't need to spend that much energy on the technical details of what you are trying to teach. We are really, really good at learning things. It's one of the ways we are all the same.
If psychology is the study of how we respond to the information around us, then developmental psychology is the study of how those responses become patterns. The goal of child development, from a practical point of view like the one in an athletic club, is to foster an atmosphere where those patterns are formed healthily and efficiently. Cognition Theory elucidates how individuals process information. As such, it can be a very valuable tool in the design of both Curriculum and Environment to this end.
The critical task of anyone who wants to build a child development focused Curriculum and Environment, as the two can not be addressed independently, is to be adequately informed as to the developmental needs and abilities of the audience they plan to address. The easiest way to do this is to identify age ranges within your audience and then identify the different developmental stages of various developmental aspects for those age ranges. You could use the theoretical model above as a rough starting point.
Design Curriculum and Environment to fit your audience, not the other way around.