When he said that, and the other three chose their opponents, the professors went from incensed to appalled. Then the unimaginable happened- Four columns, one wider than the other three rose up and were immediately covered with cloth.
The quartet clambered onto one column each, and Harry beckoned both Severus and Dumbledore onto his wider 'stage'. Confused, the pair of them clambered up. Then Harry, who still looked livid beyond measure, bellowed "Everyone ready? The Duel Starts NOW!" Hearing that, the other professors clambered on to face their opponents. When Snape drew his wand, but Dumbledore didn't, Harry added " What are you waiting for? An invitation? Get your wand out as well, Albus!", almost ending the sentence in a sneer.
Albus was shocked that Harry Potter, of all people would behave so audaciously- seemingly believing that Harry had gone in over his head, he sighed, then drew his wand. Then he said " Harry, I don't want to do this, but you must curb your arrogance lest you lose sight of the most important thing. However, you are retaliating with full force, and thus, I must implore you to reconsider your actions."
Harry responded with a confident smirk. "Just get on with it." he said. Severus had, at that point, had quite enough of the Boy Who Lived. He had immediately said "Expelliarmus!" and pointed his wand at Harry, aiming to knock him back. However, Harry simply stood, smirk in place, and didn't even budge from his position... And for good reason. He seemed completely unaffected by the Disarming Spell.
Albus sighed, then cried out "Stupefy!", then proceded to lecture Severus " Disarming an unarmed person will not knock him back! You must at least Stun to-" "Oi! Lecture him after you've won!" roared an unimpressed Harry, immediately launching into a counterattack with two Furnunculus Curses aimed at the pair, which were blocked. But the shock on both their faces was obvious- Harry neither cried out the spell, nor used awand to cast the curses, which only meant one thing- he, Harry Potter, was immensely powerful for his age, and belonged in the fifth year. The next few seconds shocked every adult who was there, as Albus and Severus were casting spell after spell, in an attempt to defeat a very relaxed Harry.
Maybe they were under pressure, maybe they felt defeat looming over them, but Albus had made a mistake- he had casted a Firestorm spell at Harry, which moved to engulf him. Harry, instead of casting a Thunderstorm spell in response, had simply run into the spell, which actually shocked the other dueling teachers, who immediately fell to Stunners from the their young opponents, who were casting nonverbal spells themselves.
The teachers rounded on Albus, who was perplexed himself, and read him the riot act for that spell. Albus had barely said "I" when a flame appeared out of nowhere, and brought about a gentle warmth. That flame slowly dissipated to show an unscathed Harry walking up to a grinning trio and congratulated them on winning their first actual duel as the Heads of House (HoH) gaped.
Then, he grinned and said "Since we, as students have won against our teachers, we think we can request you to allay all punishments that were planned for us. Now, if you will please listen, I have some important things to say. But before that, you have any questions, Albus?"
There was only one question on Albus' mind. "How did you manage to escape that Firestorn spell?" "The trick was in the timing, but I imagine you can do the same with time, sir. In any case, that would be possible for you in about-" was the beginning of Harry's (Actually Manny's) reply, but he was stopped by a shocked Albus, who said "No one can just jump into a firestorm and reappear in a flash of fire- that is a Phoenix's ability! You are simply lying and must be kept under-" "Wait, wha- you're telling me that Albus Dumbledore, Wizard Extraordinaire, hasn't discovered it at all yet!?" interrupted a shell-shocked Harry. It looked like he had been given a box full of bull-dung and asked to touch it.
Then something clicked inside his head, and he asked Dumbledore "Is your family close to the phoenix? And I mean every family member?" Dumbledore simply nodded, and Harry fell into deep comtemplation, and some words could be heard to be- "Is it?... But then... Even if so... Then that would mean..."