Disclaimer: I do not own anything related to Harry Potter. That honour is entirely bestowed on J.K Rowling.
Hermione Granger walked down to the potions classroom, feeling slightly nervous.
She had been 'dating' Severus Snape for 6 months now, but she still felt slightly nervous when she tried to do something sexual to him, as he was still her professor.
The school didn't have any problems with it, neither did the students, although quite a few thought she was slightly nuts, and she was still less experienced than him so was still unsure.
She approached the door and peeked into the classroom, and seeing Severus at his desk alone, she entered the classroom.
"Hi Sev," she said cheerfully, walking towards his desk and hugging him around the neck from behind.
"Hello Hermione, what are you…" but before he could finish she caught his lips in a soft kiss, licking the seam of his lips to tempt him but pulling away before he could react.
Hermione took advantage of his stunned silence to straddle his lap and draw his mouth in for another kiss.
At that point the bell rang and Hermione quickly hid underneath the desk as the 2nd year Ravenclaws and Hufflepuffs entered the room and sat down.
Severus was very aware of where Hermione was and that she was resting her hands on his thighs to balance herself until she got onto her knees comfortably.
He waved his wand at the board and told the class to get on with it.
Hermione considered her position for a second and a grin spread across her face. She had wanted to be in a similar position earlier but the bell ringing had prevented her from carrying out her plan, but she couldn't pass up the opportunity now.
She placed her hands on Severus's knees and slowly slid them up his thighs pausing now and again to squeeze them slightly.
She felt Severus tense up but relax as her hands got closer to his crotch, and she saw the tent in his trousers get higher as the material stretched to accommodate it.
Her hands reached the bulge and she stroked them over it on her way up to the button and zip, which she opened to reveal tented black silk boxers.
She arched an eyebrow and whispered, "Silk, nice and … soft." and she slid her hands back over the silk boxers, rubbing the bulge over and over again.
Severus gasped and a small moan escaped his throat. The classroom was noisy enough from bubbling cauldrons and the scratching of quills on parchment to disguise the noise, but any louder and it would become obvious that the noise was coming from Severus.
Hermione looked at her watch and saw that there was just 10 minutes to go until the end of the lesson so she hooked her thumbs into the top of the boxers and pulled them down and over the hard shaft.
A silly grin spread over her face as her hands slowly crept up to the erect member and wrapped themselves round it.
Severus fisted his hand and bit down on his fingers to stop the inevitable sound of pleasure to escape his tightly closed throat.
Hermione moved her hands up and down the aching hardness, trying to prevent herself going any faster and creating any noise that may arouse (no pun intended) the classes' suspicion.
Severus's fingers now had teeth marks in them from preventing him from making any embarrassing noise, so when Hermione moved her hands up and down faster, he bit down harder, feeling them pain in his fingers.
There was only 5 minutes to go now so she sped up the movement of her hands, being rewarded by a gasp from Severus muffled slightly by the fist that was still in his mouth.
With two minutes to go before the end of the lesson, Hermione took away her hands and replaced them with her lips and tongue, kissing and licking the head of Severus's member.
Severus felt his heart rate speed up dramatically and he suddenly became very hot in the heavy robes, regardless of the temperature of the dungeons.
"You should have finished by – ah – now," said Severus, has speech punctuated by a gasp. "Put your potions in a – ah – vial and – ah – place them on my desk them get out, as quick as possible."
The students didn't need to be told twice and every single one of them was out of the classroom in 1 minute. Severus pushed back his chair; Hermione's mouth now wrapped around his hardness went with him.
He watched as Hermione's mouth sunk down deeper, taking all of him in to the heat.
Severus groaned and sank into his chair, letting himself feel the pleasure mounting inside of him until he couldn't control it anymore and he exploded into Hermione mouth, moaning her name as he came.
Hermione licked him clean and put everything at crotch level back as it was and zipped up his trousers.
She came up from the desk smiling and gave him a kiss, which he responded to eagerly.
She broke off the kiss and left the room, turning just before she left the door and blew a kiss and Severus, and walked out of the door.