"Simple."
She waves her hand. Suddenly, some of the boys notice that their legs are starting to bent backwards. Some of the girls feel feathers sprouting along their arms, their fingers merging into thin tips.
In seconds, several boys are transformed into minotaurs. They quickly gather around Duane, who they recognize as their alpha. Several others become satyrs, their bodies completely covered in thick brown or white goat hair, their faces now those of large adult male goats. Naked, they turn their attention to finding food. The rest of the boys become centaurs. Thick hair grows down their backs, like horses' manes, while the rest of their bodies become that of large, muscular stallions.
The girls who are sprouting feathers quickly turn into harpies, and begin flying around the room, bumping into each other as they lack the space to move around freely. Their thick talons carve large gouges in the wooden desks, and their faces begin to push out, like beaks. Some of the other girls become minotaurs, satyrs, or centaurs, but with exposed breasts and less muscle mass than the males. The rest, about three or five, are given white Greek clothing to wear as their ears curve upwards into points, their eyes become pools of blue, green, or brown, and their hair curls into fanciful braids and buns. They join their new mistress at the head of the class, while the harpies take up positions guarding the windows and doors, before stretching their wings out to block the view for anyone outside.
The nymphs order the other beasts to begin mating. The male minotaurs wrestle with the female ones until they submit and allow the males to insert their engorged penises into them, the satyrs couple while eating green plants that spring from cracks in the floor, and the male centaurs quickly mount their mares. The room soon fills with warmth and the smell of sex, and the males begin ejaculating and cumming more than the females can take. Some get forced off, causing their sperm to shoot all over the room. Some lands on the harpies, but they show no discomfort.
The nymphs use their magic to make the males incredibly lustful and speed up the production of semen in their testicles. They order them to keep mating, so as to multiply their offspring. Some get bored and start wandering towards the nymphs, who reluctantly service them until they return to their original mates.
Finally, Ms. Yannatou decides to put an end to the coupling by having most of the males castrated. The removal of their balls causes most of the beasts to calm down as halters and ropes are put around their necks and the nymphs and harpies lead them out of the room. Ms. Yannatou is the last to go. She smiles briefly, and then shuts the door behind her.