This is also referred to as "Cold Calling"
Cold calling is different, though. Cold calling is when you call on students regardless of whether or not they are raising their hands. Sometimes the teacher may specifically call on a certain student who she hasn't heard from in a while, or the teacher may choose a method to randomly select a student to answer. In a class where cold calling is used often, you may never see students raise hands to answer a question because they're so used to being randomly called on. Of course, kids may raise their hands for other reasons, but not that.
I use cold calling in my classroom. Some teachers who visit are not super excited about it. When I've talked to them about it, I usually hear stories about an uncomfortable experience they had when they were younger when they were called on without warning. Then they say that clearly cold calling isn't good for all students because it wasn't good for them. Just because it takes someone out of their comfort zone, does not mean that cold calling is bad.
Really though, if a teacher really understands how to use cold calling in their classroom, the students shouldn't feel uncomfortable. I mean, maybe for the first few days when they're just getting used to it they would, but eventually it becomes routine. Just like any new thing you introduce to your class. A teacher who uses cold calling the right way knows how to alleviate the discomfort for even the most shy of students.
The biggest benefit is that you get to hear from all of your students. No more having a handful of students dominate all the conversations. Once your students know that this is how answering questions is going to work in your classroom, they accept that they're going to need to participate. It also raises the expectations for all students. It helps keep your expectations high. The students know they need to be paying attention because they may be called on at any time. Another benefit is that you're able to get a little more formative data on students who may not normally hear from.
First off, let me say that I don't do this all day long. That would be maddening. There are times that we do turn and talks and I hear a specific group give a great answer. I want to hear from them. I'm not going to leave it up to chance. There are times during the day that a kiddo is really excited to share an answer that they came up with. I'm fine calling on them. There are times when that one kid raises his hand - you know the one who never raises his hand. I could be in the middle of randomly selecting kids and I'd still stop and let him share his answer! There's a place for cold calling and below are some tips that I'd suggest using to help make it successful for both you and the students.
Use a tool to help decide who to call on. I've included a list of different options below. I've started using calling cards this year, and I absolutely love them!
Do turn & talks more often. This helps ease some of that anxiety for your shy students and helps them prep to give an answer in case you call on them.
Make students share an answer if called on. Have a system in place for what happens if a student doesn't know the answer. In my classroom, I tell them I'm going to call on a few more kids and then come back to them. I also reassure my students that they're able to repeat the same answer as someone else if need be.
When needed and if possible, let certain students know in advance that they are going to be called on soon. This can also help ease nerves.
Tools to Use
Names on a card or ice cream stick
Apps
Decide Now, Shake