What if The Four Founder's Portraits Trained Harry Potter?

The Room of Requirement is empty. The last of the DA members filed out twenty minutes ago, and Harry Potter stands alone in the training space, his wand still in his hand, his reflection caught in a mirror propped against the far wall. He watches himself. Fifteen years old. The boy who organised a secret army because the adults in charge of his education decided practical defence was unnecessary during a war. He runs through the lesson he just taught. The absolute fundamentals, and half the room