So this was a thing I just came up with off the top of my head. It's not suppose to be just modern, but with Spiritual things in the mix, you'll see later on. But read on:

The classroom was abuzz as they waited for the teacher to come to class. In this class, they had multiple subjects, sometimes culinary, other times shop class, but today was Human Sexuality. Aang was nervous, since this was a partner class and his partner was Katara Aqua. He and Katara shared a secret love for each other, though neither of them knew it. He tried not to shake as he sat in his chair by the olive skinned beauty while she checked herself in the mirror, making sure she embarrass herself in front of Aang. Sokka and Yue sat in front of them, he was trying to convince her to have dinner at his house during spring break to finally meet his parents. To their right, was Zuko and Suki, she was painting her nails as they both talked about their anniversary. In the front right was Mai and Jet, he was talking to her about his track record and she responded in her usual monotone voice. Lastly, in the back, Toph was talking to Haru about new techniques she had made. Roku walked into the room, "Okay everyone, quiet down. Today, we are going to talk about Human Sexuality. Now, how many of you have had sex?" No one raised their hands. He nodded, "Okay, what is the cultural perception about sex?" Katara raised her hand, "Miss Aqua."

"The Spirits say that sex should be shared between two people who truly care for each other whether it be under the sanctity of marriage or not." She answered.

Roku smiled, "Very good Miss Aqua."

"Kiss ass," Toph muttered, Katara turned around and eyed the blind earth bender.

"Anyways," Roku, regained their attention. "Does anyone know any facts about sex?" Suki raised her hand, "Yes Miss Silver?"

"A woman can achieve 5 different types of orgasms, Clitoral, Vaginal, G-spot, Deep spot and Anal orgasm." She said.

Sokka snickered earning him a elbow from Yue, he wiped a tear, "She said Anal."

Roku rolled his eyes at the immature boy, "Correct Miss Silver, anyone else know anything?" Zuko raised his hand, "Mr. White?"

"The elements we bend have an effect on our sexual needs."

"Correct and does anyone know what it is called?" No one answered, "It is called," Roku began to write on the white board, "Elemental Lust. This will be our first subject. Now, with Elemental Lust, it's all about your preference." Aang's eyes wandered over to Katara who met his gaze and they both turned away from each other, blushes covering their faces.

"Can Elemental Lust happen between two males or two females?" Yue asked.

Roku nodded, "Of course. Elemental Lust is intertwined with your love and your destiny with that person."

"I know who I have Elemental Lust towards," Jet smirked, while Mai sank in her seat.

"I'm sorry Jet, but there has yet to be a case where someone has Elemental Lust towards their hand." The class busted out in laughter as he sank down in his chair along with Mai. "I know this subject is very different from the others, but we will still do things as usual. You and your partner will grab one book for both of you and read the first chapter about Elemental Lust and how it affects teens like yourself. You will have a test on it next class." The class groaned, but Katara was first in line for the books.

"Can we go to the library to study Mr. Roku?" Katara asked, he nodded as he handed out more books.

"Wait," He said before Katara could move. Roku reached below his desk and put a basket of square objects on his desk. "I have been informed that I need to make sure all you kids are properly protected, so before you leave, I want all of you to grab as many condoms as you would like. Of course, if you haven't already ladies, remember that our boarding school gives out oral contraceptives. Even if you aren't sexually active, it's a good idea to sign up for the program to get them for free."

Sokka snickered as he and Yue got into line for the book, "He said Oral."

"If you ever want me to touch you again, you better grow up," Yue whispered. He zipped his lip as Katara's face went red as she took a condom.

"Aang come on," She said as she stood by the door. He grabbed his bag and grabbed a condom before leaving.

Sokka grabbed him before he made it out the door, "You try anything funny with my sister…"

"I know," Aang pulled away from Sokka's grasp and followed Katara. He was surprised when she took a right turn. "Katara, the library is that way."

She smiled, "I know, I just don't want to study there." His brow furrowed as continued to follow her. It wasn't like Katara to not follow the rules or lie. She lead him out of the building and into the dorms. Katara unlocked her dorm and let him in. The room had a fairly large TV on one side and a bunk bed on the other with a bathroom to the side of the entrance. Katara sat her bag by the side of the bed and pulled out the book.

"Uh, Katara, are you sure it's okay for us to be in here?"

Katara nodded, "Of course, I just think that it would be more comfortable talking about this in here than in the library." She opened the book to the first chapter. "Okay, Elemental Lust." Katara read of the parts the Roku had already explained. "It's all about someone's preference, yadda-yadda, the strongest lusts are usually…" She swallowed the lump in her throat, "…between Air and Water." The water bender looked up from the book, her gaze meeting his. "Both can be calm…" They both slowly leaned in towards each other, "Or cause great destruction." She looked at him through half lidded eyes, "And they can mix…" Their lips were centimeters away from each other. "Perfectly…" Both Air and Water met each other in a kiss, both of them feeling the passion fill each other. They pulled away slightly, opening their eyes. She watched as the storm within Aang's right eye began to fill with blue and he watched as the calm sea in her right eye became silver. Both of them felt their body temperatures rise dramatically, mostly their lower regions. Aang pushed the book away and attacked her lips, both of them moaning in pleasure. She pulled his shirt off as his hands went up hers. Once he finally got her shirt off, they looked each other in their grey and blue eyes. "Do you-" He nodded.

"Do you-" She nodded also. "I love you Katara."

"I love you too," Aang unbuttoned her pants and pulled them off her leaving her in her blue polka dot bra and panties. He pulled his pants down as she stripped out of the rest of her clothes. Once he was out of his boxers, he turned to see her lying back, naked as the day she was born. Her medium sized breasts rose and fell with her quick breathing from their passion. He could smell her wet arousal, feeling his erection throb. "Please, don't make me wait." Aang got in between her legs, but remembered the condom in his pocket. He quickly grabbed it and ripped the package open. She whined with anticipation as he rolled it on, then finally got back between her legs. Katara put him inside her and he thrusted all the way in, past her barrier and press against her cervix. To her surprise, she didn't feel anything but pleasure. Aang's thrusts inside of her were quick and passionate, both of them sharing heated kisses. Katara was in total nirvana with Aang inside of her, her fingers repeatedly massaged her clit and moved her hips against his. She switched her position and got on her hands and knees, Aang entered her from behind, going in deeper than before. Katara grabbed his hand off her hips and made him play with her sensitive nub. Their passion grew until they both climaxed and collapsed on her bed. As their lust died down, reality hit both of them like a hammer. Aang pulled out of her as she grabbed her pillow to cover herself up. He threw the condom away and put on his boxers. "So…we just…"

"Yeah." Katara noticed the blood that was on her blanket now and the soreness that was now coming to her. "So we have…Elemental Lust for each other?" Katara nodded. "You're eye…"

"Mine did that also?" She asked. He nodded. "It looks like we have to do more studying on it then…"

Her grip on her pillow grew tighter as they sat in awkward silence. "So did you actually mean what you said or was that just our lust?"

She looked up at him, "Y-yeah, did you?"

"Yeah, I really love you Katara." He leaned to kiss her but she backed away.

"I think we should learn more about our Elemental Lust before we kiss again…we might end up going nuts again." Aang nodded and sighed, grabbing his clothes. "Oh screw it." She leaned in and kissed him, but pulled away when the familiar feeling started to fill her again. "Okay, back to business."