From the psych-101 course I did in college: positive reinforcement is usually more powerful than punishment, especially in children.
If you constantly give negative consequences for any kind of bad behavior, it's true that kids will eventually learn not to do those things. And doling out a healthy dose of push-ups for misbehaving is sure to help train 'em. But what is even better is rewarding positive behavior when it comes.
So if Susie complains constantly, and you're always telling her to drop and give you five, you do need to really reward her when she finally does something right. Otherwise she'll just get used to the push-ups, her arms will get hella strong, but she won't really learn what kind of behavior you expect from her. It's not going to disadvantage the kids that always behave well, as long as you're consistent in your punishments and rewards.
I teach second graders and it's much more powerful for me to praise the ones doing well than punish the ones off task. I use an app called class dojo and students earn points throughout the day. Sometimes if they are all talking, I give a random point to myself (they don't know I have myself set up as a student) and as soon as they hear that positive ding, they all stop talking and get super focused because they want a point too.