Its important while focusing on parenting to treat your child in a respectful understanding way which will help them feel that their feelings are being heard and therefore will help them be more willing to listen when parents tell them what they should do.
Sometimes its easy to fall into a cycle of resorting to using punishment with our children, when in reality sometimes parents are too quick to enact punishment when there can be many other methods to helping children work with a child to come to a conclusion.
There is a difference between doing "to" a child, by forcing them into making certain decisions, instead of working "with" which is more effective.
Many times when a child is misbehaving its easy to tell the child what to do, by getting angrier and then forcing the child by using consequences. But in reality this will only cause the child (or teenager) to feel powerless and to then become defensive. Because no one wants to feel powerless, and generally this doesn't encourage positive feelings.
It is more effective to take a path that helps the child feel that he/she is able to part of the decision making, because that increases the chances of their choosing to follow through. Also if the child is able to pick a consequence, they are generally more likely to feel that it is fair. Partly we need to make sure that we give them choices which allows them to feel that they are able to learn to make good choices and being responsible for their own actions.
It is important to allow them to see that there are consequences for their actions, but we should make sure that they are natural consequences, and make sense based on the circumstance. It also helps if your child is able to decide with you ahead of time what a sensible outcome would be if they didn't follow the rules.
Also we should always speak in a positive way to our children, we should never call them names or label them because it causes them to feel more discouragement, hurt their sense of self esteem and ruin your relationship. Its important to focus on the action and not connect your child's sense of self worth based on an action. If a child is tired that doesn't mean they are "lazy" if a child is whining the problem is that they are probably tired and not reacting well, but we shouldn't say that they are a "whiner". This isn't respectful to the child and doesn't show an increase of love. If we need to correct we should first correct softly and lovingly, and then if they don't listen we can be more firm but always focus on showing love. Our children must feel of our love. It isn't enough for us to love or children, we need to show that love.
Sometimes I think parents are a little too worried about the grades. Many times parents mean well by trying to help their children to do well with school, but there can be cases when they are handling it in a way that focuses on the results of the grades instead of focusing on learning. We should help our children recognize that they really have abilities to get better, we should also help our children know that we will love them regardless of the grades. Then we want to be able to help them why its important to work hard in school, and be willing to help them.
There are some cases when as a parent you will need to step in and make the final decision, and be firm.
First- when it is dangerous- sometimes the circumstance is too dangerous to allow your children to make the decision that you know will harm them
second- If it will negatively affect or put others at risk
third- if the natural consequence is too far into the future.