Yachi is helping Hinata and Kageyama study for the upcoming exam.

Yachi: And this is on the exam, gotta learn this- looks at Hinata who is swinging on a chair Hinata stop swinging on the chair-

Hinata: we- oh, Yamaguchi swinging on his chair while Kageyama next to him look like he might do a seizure while learning for the exam.

Yamaguchi walks in holding another book for them to study for the exam with a bored look, Tsukishima is just reading a book. They were waiting for you too.