I just read an article about discipline in Children's Church. Most places set up Children's Church differently from Sunday School. I'm in my 50's and things were definately done differently at home, school and church when I was a child but I'm not a fan of corporal punishment. Here are some thoughts that apply in any number of situations.
A good teacher focuses on what they need to cover and how to cover it in the alloted time in a way that enables as many children as possible to succeed. I did well with preschool but otherwise I wasn't the best classroom teacher because I got distracted from my goals looking for ways to draw in individual children. We didn't always get from point A to point B. We tended to take side trips.
When we think of controlling a classroom we think "Discipline" but here are some strategies you may not have thought of:
Know every child's name and something about them. Remember something they told you about the week before and when they walk in or sometime during the class ask them (not publically, just one on one) how it's going.
A 5:1 average child:adult ratio is great if you can get it. These tips apply to every adult in the room.
Praise every child you see doing something right. Again, not publically, just one on one. You have to be watching. For some kids you might have to be keenly observant. You might even have to change what you consider "right, good, kind," Find something legitimate and positive to say. 'You have an amazing amount of energy!" But it's not that hard.
Encourage your kids to catch each other doing something right or kind, to say thank you, to encourage one another. Engage their problem-solving capabilities. Respect the fact that some kids are group people and social butterflies and some aren't. Some are pencil and paper/sit & listen politely kids. Some not so much. Not that they can't learn these skills but mix them up with more desireable activites.
Anticipate trouble and design your time, your room, your groups and activities accordingly.At least in the beginning. Let the kids draw while your read to them. Let them build with sponge blocks that don't make any noise while your read to them. When kids earn privileges, add them. When they act up take them away. Painting, clay, legos, markers, field trips... Add them the following week or at the end of class when you've had a really good week. I'm not talking about something like exercise, food, water. Timing is important. Don't wait too long. You may have items or activities that most of the class doesn't care about but someone who is hard to handle or keep focused might do anything for it.
And what about those kids? Why don't they care? What would they rather be doing instead? Why are they acting up? If they want attention and act inappropriately until they get it, then yes, withdraw attention or isolate them. But have super rewards when they're good. If they act up because they feel inadequate, without humiliating them, find tasks for them that will make them feel adequate. If they have energy to burn have parents send them in play clothes and play run around games or an active thinking game before class. If they need motivation , what motivates them? How can you weave something they care about into their class experience? Yes, we're commanded to love the Lord our God with all our heart, mind, soul, strength, but we're also commanded to love our neighbor (the kids in our class) as ourselves.
It may be that you can wait until the end of class to introduce your motivators or you may need one every 15 minutes. You can also divide your room into stations and start your groups in such a way that the kids who are hardest to motivate get the stations they care most about begining, halfway, and last through the cycle and at the end. For kids who don't even want to walk through your door you might want those activities available to them first thing. Figure out what you can use to distract a child from an inappropriate behavior to something more appropriate.
I'm not saying that there aren't times when a child just has to do what she has to do without rewards but there are ways to lay a foundation for a relationship that can handle that. I'm not talking expensive hype consumerism or multi-media but appropriate individual care & attention in a group setting and attention to individual differences. God made these kids. We might mess them up but God made them.
Don't threaten if you're not going to follow through everytime and immediately. Don't make rules you can't or won't enforce. Your kids just learn that your words don't mean anything and you don't want to teach them in a Sunday School class that words have no power. But that's a discussion for another time.