Recently, someone posted this question to an online youth ministry forum I'm a part of: “How do you handle disruptive students during a lesson or sermon?”
One of the most helpful ways I've learned to “handle disruptive students” is actually borrowed from the education world. Several years ago, a teacher friend of mine told me about a strategy called “positive reinforcement”. In this strategy, you essentially ignore negative behavior and instead, reinforce and affirm positive behavior.
Instead of stopping what you're doing every 30 seconds to tell the squirrelly kid to “Sit down!”, ignore him.
Instead of shushing the two girls constantly whispering to one another, ignore them.
Instead of explaining you're not answering questions yet, ignore the kid who's raised his hand for the billionth time.
To be sure, such an approach sounds strange, maybe even counter to what every fiber of your being normally tells you to do in this situation. Yet, this approach works because it builds upon the belief that the motivation behind disruptive behavior is usually attention. Therefore, by not acknowledging disruptive behavior, you take away someone's motivation for being disruptive in the first place.
You further reinforce this by noticing positive, good behavior in kids.
After the squirrelly kid sits through your message, thank him for his attention and ask him what he found most interesting.
When the two whisperers are quiet throughout your message, tell them how much you appreciated their attention.
When the persistent hand raiser asks you his questions after your message, thank him for seeking you out in private & reiterate that you always want to answer his questions; You just don't always want to do so in the middle of your message.
By giving kids attention for their positive behaviors, you encourage them to repeat them.
Once this pattern is established, other kids will learn that the way to get your attention isn't by acting out. Before you know it, they'll be clambering for your attention by doing good.