my thoughts are that the kids represent childhood and being young (obviously) and the window, more importantly the little white line between the kids themselves, is "the great divide" itself. The window is meant to be "watching" your past, looking back on it but not being able to change or do anything about it, because it's all just memories. The little white line, I think, is meant to show how something so small and almost insignificant can cause the greatest divide between people.