I was Adjunct Lecturer for some time in a technical field/institution and yes, I came across such type of students and situations.
What I've found out was that not strong students were feared to answer because they maybe say something "stupid" or "wrong" or anything that could be accompanied by a synonym of the previous adjectives. And, just by "luck", in such classes there always was a really good student who always knew the right answer
What I did to overcome such situations was to organize the lecture or the lab in order to actually looking for wrong answers in order to, on one hand, prove my point, and in other, motivate and make students to think about why I actually saying what I was saying in the lecture, i.e. what problem was solved with what they were going to learn in the lecture. So, if I was to point out the problem then I needed the problem and the problem was found in the wrong answers.
Thus, if the good student yield out the correct answer I accepted it. Actually, I was saying that this was the correct answer. But, just afterwards I asked "Although that this is correct, why is correct? What someone else would do? Why is wrong something else?" and trying to take answers from students that were not active in the lecture/lab. If the non-active students were not saying anything, then I asked "Why you do not say just what it comes to your mind", which most probably followed by "Because I do not want to say anything wrong". Such answer gave me the opportunity to "change the game" by pointing out really hard that "everyone is born without knowing and there are not wrong/stupid/etc answers from people that learning". When (finally) I got my wrong answer, I tried to: a) justify the student that gave that answer (because was a common answer, or an answer that was first came to mind), and b) start revealing the flaws of the wrong approach (and provide the path to the correct answer) with consecutive simple questions.
Although that such a strategy may took away some valuable time from a lecture, dialogs like the above were only held once or twice in the semester. Afterwards, most people were active and the good students were trying to actually go "deeper" in the problem than before. But, because "going deeper" required to find out what were the wrong approaches their "learning difference" from other students was diminished. This diminishing was happening because good students were actually waiting to listen my counter argument in the not-so-correct answers of their colleagues. By doing so (i.e. waiting for my counter argument), they do not yield out correct answers, they do not discouraging their colleagues and they learned to think one step ahead.