Sometimes I see teachers get into confrontational conversations with students, where the tension escalates very fast for no reason because the child is off-task first and the teacher reacts in a way that makes the child feel "picked on." In my experience, you can avoid this kind of thing by just reframing your questions to be about the work. I often teach very active, social kids, and I find that the way I phrase my questions to them often keeps them calm, focused during the class instead of letting things spiral out of control.
For example, when I am helping a kid in class and I can see a kid all the way across the room to start to get distracted, I immediately say, "[So and so], are you talking because you are completely done with this task?" I haven't yet told the child off about the fact that they're misbehaving, but I am probing into why they're doing this. I think almost always, the child responds with one of these:
1. "No... but almost!" and turns back around to resume the task.
2. "Yes! I'm finished!" in which case I quickly walk over, give them another task, and tell them either that I'll very soon come back to check on their finished work, or I point them at a person whose work I've already checked to check their answers against. The latter usually encourages peer discussion of differences and errors.
3. "No, but I need your help!" and depending on the nature of the task and how many kids are in queue waiting for my help, I'd either direct them to asking another kid for help (again encouraging peer interaction), or I say that I'll be right there with them.
(4. Very occasionally, I get a smart-alecky response like, "Yes!" when they're clearly not finished. When that happens, I always immediately ask, "So you're saying that I should collect it from you now, grade it, and move you along to the next assignment?" to which the cheeky child always mumbles, "No...")
So, I find that asking the right question when you notice a kid is talking / off-task in class is helpful in putting the kid back on track by addressing their need or reminding them gently that our time in class is purposeful.
Similarly, after a few warnings, when I decide that I do need to move a kid's seat or to put them outside the room altogether, when I approach them, I say, "I need you to move now so that I can help you focus on this task." This way, even if they feel somewhat punished, they can hear in the back of their minds what I am saying about using it as a tool to help them learn. (At the point when I do decide to move a child though, I don't allow negotiations. They cannot still try to haggle that they'll be on task "starting now.") If a child is moved outside of the room, I tell them that they can come in to ask me a question, and if I get a chance I'd pop my head out to ask if they're still doing OK. And then, after class I always tell them that I wish I didn't have to move them, that I wish they could just learn to focus on their own -- so that the child can see that I am really on their side. I make the conversation always about their learning, not about how many times I had to ask them to get on task.
When a kid exhibits continuous, repeating instances of disruptive behavior in one class (or over the period of a few classes), then when I communicate with the kid and the parents afterwards about this (which has to be immediate and firm), I still make the conversation to be about their learning. Either the child is not keeping up with the content, and I say that "I am concerned that this type of behavior is actually really damaging their learning, [with specific examples]..." or if the child is advanced compared to their peers, then I say that "this type of behavior is damaging our learning community and therefore is not acceptable." Frame your observations in a way that is impersonal. It's not about you or the child. It's about how their actions impact the task or the learning -- either their own or that of their peers. When you communicate this way, you're helping parents and children see why they need to improve, instead of just saying, "You cannot and should not be disruptive or disrespectful."
For some kids, the change is very gradual and it can take a whole year for them to learn to control themselves. But in the mean time, VERY importantly, your relationship with the kid will not be damaged by this type of confrontation. If the kid likes your lessons and likes the way you run the class, they will slowly develop respect for you, and the confrontations will thereby decrease in frequency. But, in the mean time, do not create additional obstacles for the kid and for yourself by being overly confrontational without also being explanatory... If each time the child walks into your classroom they are already antagonizing you and your approach to discipline, then no matter how great your lessons are, you're going to have a hard time in trying to win the child over.
Just some quick thoughts about discipline. Many teachers in private schools, I find, don't discipline as much as they need to, and that's a problem as well. A kid always needs structure, and as a teacher it is our duty to help them learn to be more focused, or to point out when they are not focused by assigning specific consequences like giving them gentle cues during class, talking to them after class, moving their seats, putting them outside, or contacting their parents. If you don't follow up immediately with some action, even if your lessons are terrific, kids cannot really respect your authority or they're being distracted by their less well-behaving peers, and their learning will therefore be affected.