It is Chemistry lesson in the morning.

Wan Yi is sleeping, her head on her desk.

Javan is sitting at the back of the class at Kenny's seat, i.e. the seat next to the back door.

The back door is closed.

Ms Lin is at the front of the classroom at the teacher's desk.

Mdm Oen walks past and stops abruptly as she notices that Wan Yi is asleep.

Ms Lin: (gesturing frantically towards Wan Yi, hisses) Wake her up!!!
Javan: (not knowing Mdm Oen is outside the classroom) Wan Yi, 你妈妈在外面。