His sack tingled as he watched her demonstrate on horseback for her students. He would save cleaning the stalls near the arena for when her class was in session. Now and then she would mount a students horse and show everyone what she was trying to tell them. He would drop everything whenever she did this and find a discrete place to watch. One time, he actually took matters in his own hands.
It was during a demonstration of something she called the rising trot. As she slipped her toe into the stirrup leaving one foot on the ground, her legs stretched apart. Each round cheek of her ass was separate and distinct and his mind reeled when he thought of the space between. She hopped onto the stirrup, and from this angle he could see her chest jiggle with each hop. 1,2,3, her lower leg swung up and over the saddle. He got a brief glimpse of her crotch region and squeezed his balls with his hand in the pocket of his overalls: He longed to be that saddle as he watched her split legs nestle into the leather seat.
He ducked into an empty stall where he could lean against a post and watch her through a knot-hole in a board. He unzipped and slowly stroked himself through his long-johns wondering how the hard leather saddle felt to her. Did she receive any stimulation while straddling it? Did it rub her clit or squish her labia? Thinking that it did made him a little harder.
She rocked back a bit as she squeezed her horse's sides with her calves. While riding off, she squeezed left then right then left in rhythm with the horse's walking gait. She explained to the students that the horse relies on her to set the pace. She demonstrated quicker leg squeezes, left, then right, then left. This made her hips rock ever so slightly and he could only think of her resting atop his lap doing his; riding him and squeezing left, then right, then left as his cock grew inside of her.
He pulled himself free of his work-clothes and noted he was harder than he'd been in a long time. His large, pink, bell-shaped cock-head was tight and shiny. He began to slowly stroke down, then up stopping just below the head. She continued riding around the arena, lecturing to her students who waited at the center. She discussed the premise of the rising or posting trot. That it was invented for riding long distances without getting a sore back-side. The modesty with which she phrased the term "back-side" made him want her all the more: The girl-next-door, the virgin, the innocent and pure. This image turned him on like the pictures in his dirty magazines of young women dressed in catholic school girl uniforms: Nice, but naughty.