This did the trick. Hermione's grin quickly evaporated. "What's this about Vicky?" a voice asked loudly. Hermione's shoulders tensed noticeably. She glared at Ginny who returned the look and stuck her tongue out at Hermione. Hermione turned around to face Ron, so Harry took his opportunity to approach Ginny.
"Quite a nice looking Patronus you had there," Harry commended her airily. "Beautiful creature, if I do say so myself. Never have I seen anything move with such grace and power."
"Oh shove off, Potter," Ginny returned, shoving Harry's shoulder.
"No need to get offended, Gin," Harry calmly replied. "I was merely complimenting you. You did well. Conjuring a Patronus is an extremely difficult bit of magic. You should be proud of yourself and your Patronus."
"Don't even start with me Harry; I'm not in the mood." And Harry could tell she was dead serious. He decided he should drop it before she opted to retaliate as she had done with Hermione. He dropped his teasing grin and looked at her seriously.
"I do mean it, though, Gin. Good job on your Patronus. I knew you could do it."
She searched his eyes for any insincerity for a long moment. She must have been pleased with what she found, for she smiled suddenly and thanked him. Harry returned her grin and moved on to help out others who were having difficulty. He reprimanded Ron and Hermione for fighting when they should be working. He encouraged Neville to keep up the practice and that he would have it down in no time. And he made the rounds through the class. After a while, he decided that it was time to move on.
He strode to the small stage in the front of the room and hopped up onto it. A whistle appeared on the podium as he thought of his need for it. Harry grabbed it and blew. A high pitched noise echoed throughout the cavernous room and silence descended. All attention was now focused on Harry.
"Good work, all of you. That's an exceptionally difficult spell to master. Those of you who managed a corporeal Patronus should be extremely proud of yourselves. Most of the average adult witches and wizards never progress that far with it. I encourage all of you to continue practicing the charm on your own, even those that did manage a corporeal Patronus. With the dementors on Voldemort's side," -the room flinched noticeably, but Harry pressed on -"it is only a matter of time before they start using them in their attacks. You will find it extremely difficult to cast a Patronus in front of dementors, much more difficult than conjuring one here in this room. It will take all of your focus to block out the effects of the dementors enough to concentrate on something positive, so it is important that you are ready should the time come."
"Now it's time for us to move on to the next part of today's lesson. This is going to be a very different type of lesson for all of you. I asked you all to come wearing something that you would feel comfortable moving around in, and I see that not everybody heeded my advice. I have little doubt that you will be regretting that decision shortly." The students all glanced at each other nervously, wondering what Harry had in store for them.
"You will notice that there are numerous circles marked off around the room," Harry pointed out. The students began looking around them, and it was clear that many of them had not in fact noticed this detail. "The next part of the lesson will be spent working on dodging. Death Eaters use many spells that cannot be blocked by conventional shields, and three that cannot be blocked by any shields. It is important that you all learn how to avoid being hit by these spells in the first place."
The students looked very worried at this, many wondering what it was they were going to be dodging. Others, like Parvati Patil and Lavender Brown seemed disgusted at the thought of doing any physical activity. "You will each pair up with another student. One student will stand in the small circle in the middle of the big circle. That person will be the caster. The other person will be the dodger. The dodger will be required to stay within the confines of the large circle.
"The caster will be shooting a mild stinging hex at the dodger. You should all know the spell, but in case you don't, the incantation is morsus." He demonstrated the wand movement to go with it. "The dodger is not to use any magic at all. You are expected to treat these spells as if they were Unforgivables coming at you. Ever since I was introduced to the wizarding world, the Unforgivables have been presented as an unblockable, unstoppable force. When you've got green light coming at you, you're dead. There is no defense against them… blah blah blah. Well I'm here to tell you that's a load of crap. You see green light coming at you, move out of the way. There's your defense.
"I expect everybody to take this drill seriously. You could one day end up in a life or death situation and these skills could mean the difference. Anyone who I catch casting spells half heartedly or that I suspect is not trying to hit their target will be forced to dodge my own stinging hexes as punishment. I can guarantee that you won't like it. We will work in five minute intervals. One partner will dodge for five minutes while the other casts. I will call time, then you will switch. Now everyone partner up."
Unsurprisingly, friends sought each other out for this drill. Most people ended up pairing with someone from their own house. Blaise and Daphne paired up, as did Ron and Hermione. The only noticeable exceptions to this rule were Ginny and Luna who had decided to work together despite their house differences. Once everyone seemed to have a partner, Harry spoke up again.