Part 1
The alarm rang at 7am but Jill was already awake, thinking of the day ahead, the day when she would finally humiliate her new step-sister and humiliate her in a very special place. She had been building up the tension all week in the classroom and now the classroom would be the scene of Sarah's ultimate embarrassment.
As she lay between her soft cotton sheets, she became more and more angry at the woman who had replaced her in her own father's affection and that could never be allowed to continue. Not that Sarah or their father had any idea about how she felt. All week she had been the perfect sister and daughter, going out of her way to make the older woman feel welcome. Well, at home she had; school was a different matter.
As she ran her hands down her younger, fitter body she could feel herself beginning to respond as one hand absently played with her sensitive nipples while the other drifted slowly down, over her flat tummy and down, down, between her legs to rub her hard little clit. Her eager teenage body was soon on the very edge but she pulled herself back and forced herself to go for her shower. There would be plenty of time for that later as she had a big day planned for her and her sister.
After her shower, she returned to her bedroom and began to put on the outfit she would be using to torment her sister/teacher in their last class of the day. Standing naked by her bed, she picked up the tiny pleated skirt and knew that the boys (and girls) at school would love the way her legs looked in it. Stepping into the skirt, she pulled it up her long slim legs and, pulling up the zip at the back, she finally fastened the single button on the waistband. It was well below school regulation length but Jill had already discovered that she had most of the male teachers eating out of her hand when she wore it. The effect it had on her female teachers was even more exciting to the teenage girl.
As she twirled in front of her full length mirror, she saw that the skirt flew up to expose her perfectly smooth pussy and she knew there were going to be more than a few "accidents" today when she bent over to pick up the pen she always seemed to drop when there was a bunch of guys behind her.
Next came her white blouse, again not quite regulation but it was thin cotton and covered her as it was supposed to. The only thing was, however, because it was so thin and because she had no intention of wearing a bra today, her hard pink nipples wee clearly visible through it. She fastened the buttons to the top and put on her school tie but she knew those buttons weren't going to last long once she left her father's house. She realised she was really looking forward to school today.
Looking forward to the day was the last thing Sarah was doing. All week Jill had been exposing herself more and more in class. She didn't know quite what to do about it but she knew that she had to do something. The first day her younger step-sister had flounced into her class, she had behaved fairly well and Sarah had dared to believe that the girl who had massaged her so well a few days previously was not going to cause any problems in class. What a mistake that was.
The very next day the trouble started. Jill's skirt was sitting an inch shorter than regulation length; obviously rolled up around her waist because it hadn't been that short when she had left home in the morning. Her blouse too was the regulation white cotton but it seemed to Sarah that it must be a size too small as it stretched across her younger sister's high breasts, even with two buttons open, which was definitely against the rules.
The first two days, Jill had sat in the front row of the tiered classroom, smiling sweetly at her teacher. On day three, however, she sat at the back. Sarah already knew that if a girl sitting so high up inadvertently opened her legs then she would have to divert her eyes from the white cotton panties on show. There was nothing inadvertent about Jill's show.
When Sarah looked up from the marking she had been doing at her desk, she saw Jill staring at her. She smiled at her sister, still appearing as innocent as her father thought she was, but Sarah could see a wicked glint in the girl's eyes. As she pulled her eyes away and looked round the rest of her class, she couldn't help but return her gaze to the girl in the back row.
Sure enough, Jill's legs were open but not just slightly. Sarah simply stared, mouth open, as her sister spread her legs even wider. When she did manage to pull her eyes upwards, Jill simply winked at her and then bowed her head to get on with her work as if nothing had happened. Sarah could feel herself blushing but the heat in her face was matched by the heat between her legs and she knew that Jill had flashed her deliberately.
As the bell rang for the end of class, everyone else trooped out, glad that the day was over. Jill simply walked past, talking to her friends, waving nonchalantly to her step-sister, and left the room. Sarah, on the other hand, stayed in her seat, sure that someone would be able to hear how wet her panties now were if she walked down the corridor but frightened too that they might even have soaked through. She would have been mortified if any pupil saw a damp spot on the back of her tight skirt.
The Thursday was even worse, even though Jill was back in the front row. Her skirt was even shorter than before but it was her top half that worried Sarah most. There were more buttons opened than closed now and Jill found an excuse on a number of occasions to approach Sarah's desk. As she bent down, innocently pointing out something to her teacher in her book, Sarah couldn't help but look down her step-sister's blouse, mesmerised by the sight of the girl's naked breasts and long, hard nipples.
Then came Friday. While Sarah was dreading the last class of the day, Jill defiantly walked into the classroom, her skirt rolled up to an almost obscene height, her school blouse open as wide as ever, wearing a very smug grin on her pretty face. Once more she climbed to the back row and, once more, she sat immediately opposite Sarah's desk so that when the older woman looked up she knew what she was going to see.
Only she didn't. This time Jill was spreading her legs wide as before but it wasn't her white panties Sarah was staring at; no, it was her naked pussy and Sarah's face immediately turned bright red. Shaking her head in disbelief, she forced herself to open her eyes which had shut automatically when her step-sister finally proved what a slut she was. If she thought that was embarrassing enough, however, when she managed to open her eyes once more Jill had taken her teasing to an even higher level. Sarah looked on in horror as her step-sister slipped her hand under the waistband of her short skirt and ran her finger along the length of her obviously wet slit. Staring her teacher straight in the eye, she pulled her hand out of her skirt, raised it to her mouth and licked her finger clean of her own teenage juices.
Her wanton actions caused all sorts of feelings within the pit of Sarah's stomach but also between her legs. Jill was obviously deliberately provoking her and, even though Sarah was very, very aroused she was even more angry. Something had to be done. Jill smiled at her but her teacher knew her pupil had gone too far this time.
Part 2
The last few minutes of the class seemed to last a lifetime to Sarah. She had not been able to concentrate on what she was saying at all. All she could think about was what she was going to have to say to Jill once the other pupils had gone. She kept running through the words she wanted to use in her head but none of them seemed right. How could she ask her step-sister why she was exposing herself in her class and how could she tell the younger girl to stop licking her pussy juices in her class?
Finally the bell signalling the end of the school day rang and all the pupils rose from their desk, without being asked, and made their way out of the classroom. Jill was once again acting as if nothing untoward had happened and was chatting to her friends as they made their way to the door. Sarah knew she had to intervene.
"Jill, could you wait behind for a moment, please?"
The young schoolgirl simply said goodbye to her mates and walked back to the front of the class, smiling all the time.