(Another tip for newbies and other interested readers.)
Some students don’t even bother with the “I don’t know.” Some just shrug. Others look sideways at friends, hoping someone else will provide an answer. Here’s the thing: You can’t let your students off the hook.
If Jon or Jasmine can’t answer, you might first try to provide clues. You could give Jon the first part of the answer or a big, fat hint. You might ask if another student can help Jon. If Jon remains lost, you can ask another student, shifting attention elsewhere to get the answer you need. But Jon or Jasmine can’t be left to sit in blissful ignorance.
It is NOT OK not to try. So if Jon shrugs, ask D’Andre. When D’Andre responds, have Jon tell the class what D’Andre said. However you finally manage to get that answer out into the room, make sure that Jon or Jasmine repeats the answer for the class. You might then add a question that forces Jon or Jasmine to clarify the answer. Reinforcement will help the whole class to remember.
Eduhonesty: Teachers can be too sensitive. We are taught not to embarrass students, so sometimes we move on when a student appears lost, letting that student retreat while other students step up to answer our questions. The problem arises when students take advantage of our kindness and opt out of the learning process. Too many shrugs and a kid can get so far behind academically that catching up becomes next to impossible.
Keep everyone in the spotlight regularly* so that all students believe that you expect them to be ready for class.
*A truly unusual situation, such as a severe anxiety disorder, may call for you to give a student a pass on that spotlight.