Daehyun knew it was highly immature.

He knew that at his age, he really, really shouldn't be laughing about this. He knew he was supposed to be calm and mature, but hell! Everytime the teacher said 's' a barely audible squeal would slip up his throat and he kept pressing his palm against his mouth to keep quite. Feeling an elbow nudge his side he flinched, turning his head to see Jongup's wide grin.

"I can't," the younger whispered and Daehyun just nodded helplessly, grinning back widely.