Tumblr prompt: AU in which Frank and Karen are teachers who argue a lot and whole school ships them (you can add the rest of DD team as shippers too if you want)

It would be simplest to say they had different ways of getting through to students, different ideologies when it came to teaching. It would be diplomatic to imply that they were just really passionate educators, that the arguments they got into were merely a result of wanting to help their kids. All of those things might have been true. They were true, damn it… but even Karen could admit it wasn't the whole truth.

Frank got under her skin. He really got under her skin. All it took from him were two seemingly innocuous sentences, and suddenly she was hot under the collar, her cheeks warm, eyes sparking. The teacher's lounge was his favorite sparring ground. He loved to lean his hip on the counter, a cup of freshly brewed coffee in one hand, his free thumb hooked into the belt loop of his jeans. It had to be a power pose of some kind, the way he just oozed confidence standing there like that.

This morning wasn't any different. She fought the urge to turn around and walk right back into the hallway when she saw him there. He hadn't said a word yet and she already felt her hackles rising. He had his eyes closed, taking a moment to inhale the rich aroma of the coffee before he sampled it. She watched him, awkwardly frozen in spot as he savored the hot liquid, his tongue darting out to catch a stray drop at the corner of his mouth. Karen felt a searing stab of desire shoot through her.

Snapping out of her daze, she threw up her defenses, stomping over to the counter. It was never easy with him, and this penchant she had for getting lost in her own thoughts, the places her mind went when she allowed it to contemplate the lines of his body, well, it wasn't helpful at all.

His eyes flew open at the sound of her approach. She didn't have to look up to know that there was a particularly unsettling gleam in his eye, that the corner of his mouth had already twitched up in an irritating little smirk. "You're here early, Miss Page. Trying to get a jump on those STP's? Last year was a bit of a disaster for you I hear."

She cut him an icy glance, refusing to acknowledge him until she had some caffeine. Pouring the coffee slowly, she stirred in some sugar and cream before turning to him with an icy glare. "Standardized tests are ruining the american education system. My kids were smart last year and they're smart this year. No matter what some stupid test says."

He shrugged, taking another leisurely sip from his cup. "Maybe if you'd spent more time having them do those practice exams I forwarded you, instead of talking about feelings and taking field trips to Central Park, there wouldn't have been a problem."

She ground her teeth, huffing out an angry breath through her nostrils. "I swear to god, don't mention those stupid practice tests again."

Frank set his mug down, frowning at her. "Can't argue with results."

They'd argued about it for weeks, and she'd flat out refused to have her students sit for hours answering the same questions over and over just so they would score high later. She wanted them to actually learn things, to be curious about the world around them. She didn't want little automatons who only knew a specific set of answers. She was ready to open up this argument, yet again, but Frank just sighed and dropped his shoulders.

"Listen Page, you don't realize it, but your job is on the line. I know you care about those students, but the school board only cares about results, because those results get them funding. It's always about money, babe."

She blinked. That had never happened before. He'd never backed down. In fact he always seemed to relish getting her more and more wound up, until she was red-faced and panting with her anger. On more than one occasion they'd drawn quite the crowd of onlookers before she'd slammed down her books and stomped out of the room. This was different, and she wasn't sure how to respond.

She cleared her throat. "Uh, don't call me babe."

"Did you hear anything I just said? You could lose your job." He took a deep breath, looking a little nervous for the first time since she'd known him. "I, uh, like having you here. It'd be a shame to lose a passionate teacher because of this bullshit bureaucracy."

Her eyes widened. How had she not realized how close they were standing? He was inches away from her, gazing intently at her as he waited for a response. She was looking at his lips. They were parted slightly, expectant almost, like he was waiting for her response so he could lay into her again.

"You'd miss me?" The words were out of her mouth before she had even thought them, echoing off the walls of the tiny room. As soon as she realized what she'd said, she felt the heat of a deep blush creeping up her neck. Frank's eyes flickered down to the vee of her blouse for a millisecond, and Karen nearly whimpered at the sudden urge to close the space between them.

She fought it, swallowing hard as she took a step back. "Listen, Frank…" She trailed off, realizing that she never really used his first name that much, derisively calling him Castle when she talked about him with her friends, using 'Mr. Castle' to his face. The name suited him, no beating around the bush, straight and to the point. She took a deep breath before continuing. "I know last year I was too stubborn. Believe me, Superintendent Ellison tore me a new one when those results came back. No matter what you think, I'm not an idiot, okay?"

He laughed, exasperation mixed with disbelief. "When on earth have I ever said you were an idiot? You're one of the smartest teachers in this place. And the way you connect with those kids, god, they are completely infatuated with you."

He almost sounded envious. Karen's eyebrows shot up in surprise. "What? But you are constantly giving me shit for the way I teach."

He smiled at her, this time fully. It reached his eyes and stole her breath away. Holy hell this was bad. Karen involuntarily took a step toward him.

"You call it giving shit, I call it spirited debate." Frank reached up and brushed back a strand of her hair, letting his thumb trail along her cheek. "I like seeing you all riled up."

"You asshole." The insult was whispered softly, trembling as it tumbled from Karen's open mouth. Reaching forward she hooked one hand behind his neck and jerked his lips down to hers.

He tasted like the coffee he'd just drank and one of the cigarettes she knew he liked to sneak behind the gym between classes. The tiny hint of desire from earlier uncoiled in her body, twisting around in the pit of her stomach before stretching out through her limbs. She pressed up against him, whimpering at the feel of his hard body unyielding against her curves. His hands found her ass, squeezing gently as he pressed her even closer, their hips perfectly aligned. The feeling was downright sinful, and Karen forgot where she was.

Panting, Frank took control, pushing her up against the counter, one hand sliding down the length of her thigh as he prepared to lift her off the floor.

"No fucking way! I knew it!"

Karen and Frank broke apart, both looking dazed and more than a little embarrassed. A fifteen year old girl was standing in the entrance to the lounge, a huge grin splitting across her face.

Karen was the first to regain composure. "Watch your language, Ellie."

The girl rolled her eyes. "Puh-lease. Like you and Mr. Castle weren't about to get down and dirty." She popped the gum she was chewing, eyes sparkling with mischief. "Matthew owes me ten bucks. I told him one of you would finally make a move."

And with that she darted back down the hall, fingers flying as she texted her best friend. Karen dropped her face down into her hands. "Oh my god, this is awful."

Frank simply shrugged. "You didn't know there was a betting pool? I had you down to make the first move next week. It's a shame too, because it was ten to one odds."

"What?" She nearly shouted the question at him, eyes bugging.

He reached forward and pulled her back to him, kissing her gently this time. "Karen. I'm kidding." He mumbled the words against her lips, brushing soothing circles against her back.

The ten minute warning bell rang. Karen regretfully pulled away from him, straightening her blouse and donning her most teacherly voice. "Mr. Castle, this is a highly inappropriate place to engage in such… activities. I think we need to meet somewhere after hours to discuss this... incident."

She flashed a sidelong glance at him before turning to slip out the door. He called out after her. "Josie's at six?"

She shook her head. "My place, five o'clock sharp. Don't be tardy."

And with that she was gone, leaving Frank to spend the next ten minutes diligently thinking about baseball and the mole on his brother's ass. Anything so that he wouldn't walk into his first period History class in an embarrassing physical state. Five o'clock couldn't come soon enough.