Kids can shut up in your classroom. They can shut up because they're too nervous or embarrassed to get it wrong. They can keep quiet because they're too scared to say “I don't know.”
Or, they can speak up because the environment is comfortable with failure. They can say “I don't know, yet”. They can raise their hands with confidence, because they know that even if they're wrong, their fellow classmates and teacher still value and respect them.
The classroom environment isn't their choice. It's yours.