The quiet student may need time to prepare a thought before sharing it.

Silence in a classroom is easily read as absence, though for many people a thought has to be assembled before it can be spoken. In a fast discussion the currency is speed of production, so the ones who need a moment never reach the floor at all. What they were holding is often the more considered answer. Quiet is a way of processing rather than a shortage of it.

Put the question first and the silence after: a full half minute before anyone speaks, or a minute of writing. Invite people by name once the pause is over, never during it.