Look at the process by which children learn to swim. Children move effortlessly from exploration and free roam to structured but simple games to taking on rigorous challenges. Here are three thoughts.
First, imagine how stunted and crippled and punitive the learning process would be without the exploration and play phases.
Second, imagine how the first two phases would be implemented in a traditional state-run industrial school - with tests and metrics and "teacher and student accountability."
Third, and most importantly, from math to biology to business to engineering, and for all ages, the greatest challenge for all instructors and coaches is to create situations and learning environments that allow for not one or two, but all three phases to happen.