Finally, with this last ingredient, I should be finished, Samantha thought to herself as she slowly, carefully began to pour the liquid from a test tube into a beaker sitting on the lab’s counter. The liquid from the tube splashed into the beaker, and at first, the reaction was just what she expected. Unfortunately, the new mixture began to bubble and rise, eventually pouring over the top of the beaker.

"No, no, no, no, no!" Samantha panicked as the liquid slid down the sides of the beaker and extinguished the flame coming from the Bunsen burner below it. "What am I doing?” she asked out loud as she took off her safety gloves in order to remove her glasses and rub her eyes. "There is no way that I’ll be able to get this right by the time Mr. Jackson comes in."

Samantha was supposed to conduct a private lab test with Mr. Jackson in order to bring up her chemistry grade before graduation. All of her grades were stellar, with the exception of her weak chemistry grade, thanks to having a bit too much fun at a party the night before her last test. Getting into a good university rested on being named valedictorian when she graduated, so she was willing to do anything she had to in order to get this final grade.

All of the frustration was causing Samantha to feel warm, so she decided to remove her black sweater with the school’s golden crest on it. The school had axed their dress code after a long court case regarding freedom of expression, and thus no longer required students to wear a uniform. Her mom had insisted that she continue to wear the uniform though, saying that it looked just like the thing a ‘Good Christian girl’ would wear to school. In reality, Sam had continued to wear it, like most of the other girls at school, because she thought the whole schoolgirl uniform thing was sexy.

The uniform consisted of a short-sleeved, white blouse, a bluish plaid skirt, knee-high white socks and black ballet flats. Whenever Samantha got to school, she undid the top three buttons of her shirt, exposing the top of her bra cups, usually an easily visible color like hot pink, and she hiked up her skirt, so that the start of the curves of her ass would be showing. Depending on how sexy she was feeling on a given day, she would also slide her panties off and put them into her bag, but instead of stuffing them all the way in, she let them hang out of an opening in her backpack. This had the effect of making the school’s boys, and male teachers, wonder if the panties hanging out of her backpack were simply an extra pair to change into later, or was she not wearing any underwear at all.

Samantha was eighteen, about five foot eight with shoulder length blonde hair, creamy white skin, and dark blue eyes. Her ass was small, and her tits weren’t much bigger, perhaps B’s, almost, but thanks to her thick, plastic frame glasses, her school uniform and good grades, there was no shortage of boys that wanted to ask her out. Apparently, the ‘sexy nerd’ thing was still big, and it wasn’t like Sam wasn’t attractive to begin with, but her nerd status certainly helped make her even more attractive. Guys seemed to think smart girls like her weren’t very experienced at sex, if at all, and as such, a girl like her was sexier in an innocent kind of way. Little did they know, girls like Samantha knew what they were doing; they just liked to tease boys by pretending to be good little nerds.

Looking at the clock hanging in the front of the lab, Sam saw that it was about thirty minutes until Mr. Jackson was supposed to come by and administer the lab test. Samantha knew that she was too flustered to keep working, and if she forced herself to continue, she would just waste time and materials in multiple failed attempts. She desperately needed to relieve some tension before Mr. Jackson arrived. Pondering ways to relieve said tension, something radical, but also sexy in a dangerous kind of way, popped into her head.

Sam looked around the room. She had entered the lab with a key and the door locked behind her. One of the benefits of being such a good student is that the teachers often trusted her with things that no other student would be, including a key to the science lab to practice before a test. According to the schedule posted on the front door of the lab, no one was scheduled to be in here for the rest of the day, and the front door’s window was covered with papers showing students what kinds of jobs they could get in the field of science. There was still a door with an uncovered window on it that led to the science teachers’ offices, but at last check, no one was in, since the end of the day was approaching, and students weren’t allowed into that area.

Pretty sure that she wouldn’t be interrupted, Sam spun her stool to look at all of the lab supplies inside of a cabinet with a glass window. She opened the cabinet and selected a small glass test tube from a rack on one of the shelves. Turning it around and inspecting it, she thought about it for a moment before finally speaking to herself.

“Well, why not?”

Samantha’s skirt was so short that it made for easy access, especially since she wasn’t wearing panties either that day. She sat back on her stool and spread her legs, letting her right leg hang off of the side of the stool, while the other one was perched onto her workstation’s counter for balance. With a deep inhale and exhale, she took the test tube and inserted it into her pussy. A small moan escaped her lips and she started to slide the tube in and out of herself slowly, the glass tube sliding effortlessly back and forth through her wet pussy lips.

"Oh my god," Sam whispered as she started sliding the tube in and out of her pussy faster.

As she used the tube to masturbate, Sam started to think about her friend Angie’s younger step-sister, Harper. At first, she only thought about how the seventeen-year-old and she happened to randomly start talking about different types of dildos somehow. Harper had mentioned how much she enjoyed using one that was made out of glass, given how smoothly it glided in and out of her pussy, allowing her to masturbate as fast as she wanted, no matter how wet she was, or was not, since the glass offered no friction, like a rubber one might if the user wasn't lubricated properly.

At first, Sam was hesitant to go out and buy one of the glass ones, seeing as how they couldn’t vibrate, and they were a bit expensive. Now though, she knew why Harper liked glass so much: the feeling of it sliding so smoothly in and out of her pussy, lubricated only by her own fluids, felt amazing. I have got to get a glass dildo of my own soon, or just book the science lab once a week and come use the test tubes she joked to herself.

It was thinking about their conversation on glass that Sam's thoughts had started with regards to Harper, but they didn't end there. Eventually, she began the have visions of Harper undressing in front of her before walking slowly, seductively towards her and pressing her bare breasts into her face. While Sam would start to suck on Harper’s nipples, the other teen would let one of her hands slide under Sam’s skirt and start to finger her pussy.

“Mmmmmm...”

Sam let out a soft moan, breaking from simply inserting and removing the test tube from her pussy to use the end of it to massage her clit with small circular motions. Over time, the test tube teasing her pussy became one of Harper’s fingers. She had been attracted to girls before, but she hadn’t been as turned on by the thought of another girl until then. Something about the younger teen’s sexual freedom, her easiness when it came to talking about sex despite her religious upbringing, something that the two of them had in common, really turned her on. While Sam felt stymied by her religious upbringing at times, Harper didn’t let it hinder her ability to enjoy sex as she saw fit, something Sam really envied.

It wasn’t long before Samantha wanted to try something else, something more... substantial. She slowly removed the test tube from her cunt as if Harper were slowly removing her fingers to tease her, and went back to the storage cabinet. After a few seconds, she found what she wanted: the jumbo-sized test tube, the biggest of the lab’s glass test tubes. The tube was eight inches long and almost two inches wide. She knew that she probably wouldn’t get all eight inches into her, but she wanted to feel something reach the end of her cunt, and the width of the tube would also stretch her pussy walls and make the sensation even better.

Samantha sat back on the stool and spread her legs. With a deep breath, she started to push the larger tube into her cunt, past her swollen pussy lips that were burning with the desire to have an orgasm and spurned on by thoughts of her friend’s seventeen-year-old little sister. Harper may have been a year younger than she was, but the teen definitely knew more than she did when it came to sex, including self-gratification, and that was really turning Samantha on.

As the larger tube was pushed into her pussy, the walls of her vaginal canal contracted at the feeling of something so big trying to push past them, making it harder to fully insert the tube, but also making it more pleasurable at the same time. ‘A little pain makes the pleasure all the more enjoyable,’ Harper had once told Samantha. True enough, with a little pushing, Sam managed to squeeze the smooth, rounded end of the tube to the very back of her pussy, and the little bit of pain she was experiencing changed to a feeling of such intense pleasure that it made her shudder. The pleasure became so much that she actually forgot that she was masturbating in one of the school’s science labs and instead was so convinced that she and Harper were alone together in one of their bedrooms.

So many of the things that she had learned about sex and masturbation came from the younger teen, as the two of them shared the reality of having religious families who would never talk about, let alone condone, such behavior; the two teens, or at least Samantha, had found someone to share their dirty, sexual secrets and desires with. Although I wouldn’t be surprised if Harper had others that she’s shared her dirty thoughts with, or enacted with, already. If only I was as free as she is, and if only she knew how I feel about her, Samantha mused.

She started sliding the test tube in and out of her pussy at a medium speed, imagining that Harper had undone her blouse, pulled down her bra and started sucking on her nipples as she continued to play with Sam’s clit. She imagined the red-haired vixen removing her lips from her nipples and smiling at her before starting to lower her face, and the rest of herself, to the floor. As she knelt in front of Samantha as she lay on the bed, Harper flipped up Sam’s skirt and gently spread her legs. With a final smile up at Sam, Harper’s face disappeared in between Sam’s legs.

Despite the fact that Sam knew what Harper was about to do, she was still taken aback by the feeling of the younger teen’s tongue as it made contact with her pussy. She gasped, both within her fantasy and in real life, as she imagined Harper starting to go down on her, at first licking up and down the warm, wet walls of her pussy, before starting to focus more and more on her delicate clit, as if she were teasing the other teen and trying to make her beg to keep her tongue on the most sensitive part of her body.

"Oh, Harper! Oh yeah, your tongue feels so fucking good. Please, stay right there, right ther- ohh!" she said out loud, perhaps a little too loud. This was followed by an even louder gasp as she started ramming the tube into her as fast as she could without hurting herself, causing her breaths to became a series of ragged ah, ah, ahs.

“Ah, ah. Oh, Harper, I’m gonna cum, I’m gonna cu- aah!” With a final cry of pleasure, Samantha came as the test tube once again slammed into the deep end of her pussy. She kept slowly sliding the test tube in and out of her pussy as she gradually came down from the momentary high of her orgasm, and her fantasy about Harper.

“Oh, Harper. You have no idea how much I needed this.”

Sweet juices poured over the test tube and ran down Samantha’s fingers. While Sam had tasted the pussies of two other girls, she had never actually tried her own. After a moment of hesitation, she ran a finger over the lips of her pussy and raised it to her mouth. The taste was good, dare she say even better than the other girls she had tasted. She giggled in response to the fact that she liked the taste of herself more than the other girls, but her giggling smile soon turned into a sad pout as she lamented the fact that was tasting herself and not Harper, like in her fantasy.

I have to find a way to hook up with Harper. Maybe I can leave something at Angie’s place, call her house when I know she’s out, and ask Harper to bring it over herself instead of waiting to give it to Angie because it’s an emergency. From there, well, I’ll figure something out, and she giggled again.

As she licked her fingers clean, she heard a noise over by the door that led to the teachers’ offices. She quickly composed herself and went over to the door. She opened it and found no one there. As she was about to dismiss the noise as nothing significant, she noticed that there was some kind of milky goo on the doorknob of the side of the door that led to the offices.

Curious about the mysterious goo, Sam scooped some of it up with a finger and smelled it. The substance smelled familiar, but there was only one way to make sure that she knew what it was. She lifted the finger to her mouth and sucked the goo off of it. The substance was indeed what she thought it was: cum. Someone must have been watching her while she masturbated.

But students aren’t allowed in this hallway, Samantha thought. And all of the science teachers have left for the day, well except for- She stopped dead in thought. Mr. Jackson, he was supposed to administer my lab test at 3:30 pm, but it’s only- She stopped in mid-thought once again to check the clock in the lab. The clock said that it was 3:34 pm. Oh my God! I must have gotten carried away thinking about Harper while I masturbated and lost track of time. If Mr. Jackson was on time, then he could have seen me masturbating in the lab while I waited for him.

At first, Samantha was worried that she was going to be in big trouble, possibly even suspended, or at the very least, Mr. Jackson would refuse to administer her lab test, and then she wouldn’t become valed- Just as that last thought crossed her mind, something else dawned on her. If Mr. Jackson had indeed caught her masturbating inside the school’s science lab, then why didn’t he enter the room and tell her that she was busted? More importantly, if he was indeed watching her, was that his cum that she had found on the doorknob?

A smile of recognition crossed Samantha’s face. If Mr. Jackson truly is the only science teacher left at school, it stands to reason that given she heard the noise at about 3:34, and Mr. Jackson was never late for classes or meetings with students, then he was the one who made the noise at the door. Furthermore, if he was indeed on time, or early as he often was, then he had spent at least four minutes watching her masturbate through the door’s window, AND he must have been masturbating to her, which then led to the ejaculate that she found on the doorknob.

Samantha’s smile widened. If Mr. Jackson likes to masturbate to me while I masturbate, then I’m sure he would be open to even more... intimate, teacher-student interactions between the two of us. Sam’s ruthless, grades-at-all-costs instinct kicked in. Screw the lab test, I’ll just plain screw Mr. Jackson to get the grade that I need to become valedictorian.

The devious teen walked back to the doorknob and scooped up another finger’s worth of cum and stuck it into her mouth. The cum may have been cold by then, but she still enjoyed the taste, and she looked forward to tasting more when it came out hot and fresh from Mr. Jackson’s cock. After all, if her friend Harper had been able to pass all of her courses this year by fucking all of her teachers alone, then she was sure that she would be able to get one good grade out of Mr. Jackson. Harper, I think you’re the true genius between the two of us.