A desert tribe had a audit hood rite bring their teens to a lake split between blue rocks and pink rocks, those that entered the blue side came back men and those that entered the pink side came back women, it was a small tribe and soon founded a town to make and sell things to the growing number of settlers and the magic lake was forgotten. A clothing factory was built were the blue and pink stones meet drawing water from the lake to wash the materials the clothes are made of.
The people making the clothes were unaware that the clothes were being washed in magic.
A high school had ordered gym support clothes from the factory but some how when delivered their was a mix up boxes of girls sport clothes were delivered to the boys locker room and boxes of boys clothes were delivered to the girls locker room.
"Kids come get the new equipment" says one of the gym teachers. The teachers steep back from the boxes as the kids rush in. Tops were in one box and bottoms were an other box, each students grab both boxes.
In the girls locker room some open the tops first and some the bottoms first. The girls who opened the tops first keep their bras on as they try on the tops, their shoulders grow wider, the girls who opened the bottoms put them on under their panties, dicks and balls grow under their panties. The girls that had put on the bottoms put on the tops and their shoulders grow, the ones that put on the tops now put on the bottoms and grow dicks and balls.
In the boys locker some boys open the tops and some the bottoms. The boys that put on the tops grow breasts from middle B cup to middle C cups. The boys who open and put on the bottoms, their hips and asses grow out, their waists pull in, pussies, wombs and ovaries grow inside them. The boys who had the bottoms on put on the tops growing breasts from middle B cup to middle C cups. The boys who put the tops on first put on the bottoms and changed in the same way their classmates did.