Five minutes later, to the surprise of precisely no-one, Hermione had a working Shield Charm. While Leo took Harry and Ron through the wand movements until they could get it right, he set Marisa to testing the strength of Hermione's shield.
"Expelliarmus!" cast Marisa. "Petrificus Totalus! Locomotor Wibbly!"
The shield absorbed the first spell, wobbled under the second and was shattered by the third.
Hermione looked somewhat crestfallen, but she quickly cast another Shield Charm, this one holding up a lot better and surviving five spells before Marisa managed to shatter it. Harry got the spell much quicker than Leo had been expecting, and before long he and Hermione were firing spells at each other's shields, with Marisa adding the occasional jinx into the mix.
"I think you can go and join the others, if you like, Marisa," said Leo.
Marisa nodded and ran the short distance across the grass to join Terry's group, while Leo took Ron through the wand movements again until finally the shimmering magical shield began to appear.
"I did it!" said Ron with a smile. "Take that, Hermione, I did it!"
If Hermione had been Marisa, she would have fired a jinx and shattered the shield, but she wasn't. "Well done, Ron," she said with a smile.
They kept going until Hermione's shield could reflect some of Leo's hexes and stand up to five or six in a row, and Harry's wasn't far behind. Ron, too, was fast catching up.
"I want to see you duel against someone you're evenly matched against. Harry, Hermione, against each other?" asked Leo.
They nodded and bowed to each other.
Harry opened with a Disarmer (strong but predictable, and the aim a little off) while Hermione immediately flung up a shield to block the inevitable volley of hexes (too defensive, but a solid strategy if your opponent hadn't learnt any shield-breakers).
Harry fired a few jinxes into the shield, putting as much power into them as he could and dodging the reflected Jelly-Legs. On his fifth spell, Tarantallegra, it shattered. He had the sense to follow up instantly before Hermione could adjust, firing off a quick Full Body-Bind which Hermione barely managed to dodge.
From that moment the initiative in the duel was firmly Harry's: his rapid-fire jinxes and hexes kept Hermione too busy dodging (clumsily; it was clear she hadn't worked much on her physical fitness) so she didn't have time for another shield and it was only a matter of time before a Disarming Charm finally connected.
Harry grinned in triumph.
"Good work, both of you," said Leo. "Once you've learnt a few more spells for these situations you'll be giving me and Marisa a run for our money."
"Did someone say my name?" said a voice from behind him.
Leo whirled around, but too slowly to block or dodge Marisa's Full-Body Bind. His arms snapped to his sides and he fell like a board.
If looks could kill, Marisa would have been vaporised in that moment.