In Thursday's Ravenclaw class, Voldemort taught them Ravenclaw's approach to Defense Against the Dark Arts:
Wisdom wins!
In fact, this had already begun circulating in the upper-year classes, and many younger Ravenclaws knew about it too. But they could only understand it fully when Voldemort himself explained it.
Unlike Gryffindor's "recklessness" and Hufflepuff's "diligence," Ravenclaw's wisdom was more like an art of war:
Know yourself and your enemy, and you will win every battle!
Be prepared for danger even in times of peace!
The general idea was to increase their overall understanding of things, consider problems from a long-term perspective, and avoid fighting unprepared. That was the guiding principle.
In practice, that meant they had to learn both "recklessness" and "diligence."
It was a tall order, and the other Houses might not be able to manage it. But for studious, intelligent Ravenclaws, it really wasn't a problem.
As long as they could sort out their thoughts and make a study plan, Ravenclaw could always demonstrate superior wisdom.
So they developed combat techniques for all kinds of situations and put various practical exercises on the schedule. Ravenclaw, a House that had never stood out much in battle, suddenly burst into a wave of enthusiasm for practical combat.
Headmaster Flitwick had mixed feelings about it. As a dueling expert, he naturally hoped the children in his House would learn from his skills.
But if the children became too restless, they might end up following the path of Gryffindor...
What a headache, what a headache, what a headache. His prized pupil had caused him a huge mess.
Voldemort, of course, didn't care about Headmaster Flitwick's worries. He only cared about starting fires.
Whoever was Head of House could deal with putting them out. He wasn't paid for that, so he wasn't going to