For my elementary-school-age children, I care more about whether or not they love going to school than I do about their academic progress. I am clever enough to know that if they are enjoying themselves at school, they will learn. Academics follow naturally if the proper environment for learning is there.
When the learning environment becomes very serious and relies heavily on assessment and grades, learning targets and goals, it is not as enjoyable. It is “work,” and children don’t enjoy work. It’s not in their nature to enjoy work; children are created to learn through play.
What defines “play?” Any activity that engages the imagination and creativity, two skills that lead to innovation and problem solving when practiced often enough.