She lets him

Yasmin was practically frozen with fear. She glanced down briefly spotting Joe's hand on her exposed thigh, before quickly looking away, her eyes catching sight for a moment of Steph's exposure, her mind racing, telling her that in seconds that would be her.

Staring at Miss Sullivan's back, she felt the skirt slide up, higher and higher, until she knew that her pubic hair had to be on show to the boy beside her.

She shivered for a moment, trying to focus on what the teacher was saying, all the while aware that Joe's hand was still resting on her bare thigh, his fingers gripping the flesh both worryingly close to her pussy, and preventing her from being able to pull her skirt back down.