In both kindergarden and first-year university, students are learning to function in a new environment. They must discover what's expected of them before they can do what we expect.
In both kindergarden and first-year university, some students are very reluctant to speak up, because they don't feel intellectually safe (they're afraid of saying the wrong thing). We need to find ways to build their confidence, not in being right but in the value of not (yet) understanding. This problem is much worse in university than in kindergarden. That's probably because learning how to do new things is what young children do (they're used to succeeding), whereas high school somehow shifts their focus to being concerned about failing to learn at the expected rate or under the given circumstances.