The Hogwarts express rattled on down the tracks, smoke puffing from its shining funnel as it steamed deep into Scotland. It was the first day of the new school year, and within all the students of Hogwarts were laughing and chatting together as they prepared for another year of magical studies.

Well... almost all of them. In one of the compartments, Hermione and Ginny were having less than a good time. They were putting on their school uniforms for the first time after the long summer, and finding it rather more difficult than they'd expected.

"Ginny?" Hermione asked, puffing for breath, "Did Mrs Weasley mention anything about accidentally shrinking our uniforms? Perhaps while she washed them?"

"I don't think so..." the other girl puffed. Ginny was stood on the opposite side of the compartment, breathing almost as heavily as Hermione was, "I bet you a Sickle this is a welcome back prank from Fred and George. I'm gonna hex their eyebrows off if it is. "
"Maybe," Hermione said, frowning, "Let's give it another go before we start scorching eyebrows though, alright?"
"Okay."

They both sucked in their stomachs as much as they could, then quickly tried to button their school skirts, tugging the two flaps together with all their strength. For a few moments the two girls tottered there, all their energy on fastening their troublesome uniforms – then finally with a great heave and a rather unladylike grunt, Ginny managed to slip the button home under her belly. With a little crow of victory, she stopped sucking in her stomach; the great pressure on the waistband caused the fabric to creak alarmingly, but it held.

Hermione, on the other hand, had no such luck. Even pulling with all her strength, the button was still a good inch and a half from its destination, the sheer girth of her midsection rendering the task physically impossible. Even if she could, by some miraculous feat of strength, get the thing buttoned, she'd probably lose the blood supply to her legs. She gave up and collapsed onto a seat, scowling with irritation. After a moment to catch her breath though, she wriggled out of the skirt entirely and picked it up.

"Well, I suppose a little early practice can hardly go amiss," she said, drawing her wand from her clothes bag.

"What're you doing?" Ginny asked, still trying to get her own skirt even remotely comfortable. The waistband was cutting into the soft flesh under her belly and it was already pretty sore; she dreaded how it would feel after a couple of hours.
"Well," replied Hermione, "I was reading the Standard Book of Spells for this year over the summer. You probably saw?"
"Yeah. You were studying from that thing half the time you were at the Burrow."
"Well it turns out I'll be using one of the spells in it rather earlier than I'd expected."

She had taken out her wand and was kneeling over the skirt. She tapped it twice, then muttered something that sounded like "espandere aksis". Ginny watched as the skirt grew, but not in all directions as with an 'engorgio' charm - only around the waistband. After a second, the growth stopped.
Hermione picked up the skirt again and pulled it on. It fitted near-perfectly, and she looked rather pleased with herself. Ginny watched enviously as she buttoned it with ease. If only she knew that spell...

Together they pulled on their shirts and jumpers, which also seemed to have tightened a bit around the middle and chest. They didn't prove nearly so troublesome as the skirts though, so they finished dressing without too much trouble and examined themselves in a conjured mirror.

Ginny pulled her jumper down to cover her stomach, but it almost immediately sprang back up to reveal the pale roll of flesh that poured over the waistband of her absurdly tight skirt. She sighed; once they got to Hogwarts they could change into their spare uniforms, but for now this would have to do. Together, they returned to the compartment where Ron and Harry had finished changing long ago.