Privacy is something everyone needs, children included. Children also need supervision. Information on balancing protection and freedom.
Children need privacy""it is an integral part of their development. Nobody wants to be watched 24/7, people simply need time alone for different reasons. Just as everybody has a right to keep their intimate thoughts to themselves, they also have a right to keep some of their personal activities private. Unfortunately, some personal activities can be dangerous to your children/teens and to those around them. As in everything, a balance must be found""there's simply no alternative.
Many parents will find that they can keep a fairly close eye on their younger children (since they need less privacy than do teens). Obviously when they are old enough to bathe and use the bathroom for themselves it's time to remove yourself from supervising those particular activities. As they grow older, they'll need more time on their own. You may try having them keep the door open when they're playing in any particular room so that you can hear if something breaks or they get hurt. Keep a close eye on them and their friends (because you are liable for their friends' safety too).
When your children get older, allow them to shut their door when they are in their room. As pre-teens and early teens, you do not even need knock upon entering. Yes, you think you've done a good job raising them, but the best parenting around can't keep some people out of trouble. This isn't to say that your child is smoking pot in his spare time, but you might use the potential of your walking in at any time in order to encourage him not to do things you would disapprove of.
Later, however, when you know that your child has been raised well and is a good kid, when you know he won't be doing drugs or building bombs, then is the time to knock before entering. Your teen should see this as a sign of implicit trust. After all, you can't just run over to your kid's college dorm and enter his/her room at any minute. No, you need to have done all your parenting before they leave.
Problems crop up when parents don't respect their child's privacy. Sometimes people just want to be alone and it is insulting if your parents don't trust you. No parent in their right mind would walk in on his/her 16 year old son/daughter taking a bath. That's preposterous. Privacy is utterly important, especially in when taking care of personal hygiene.
As a parent you are legally responsible and can be sued for your child's actions (in some cases at least). Here is a prime example. Why did their parents not check in on them from time to time? If your kid is building a bomb, they can't hide everything in the time it takes for you to knock and open the door. Give privacy, but be reasonable.
My advice to teens would be not to betray their parents' trust. If your parents ever walk in on you doing something you shouldn't be doing, you can fully expect all your privacy (except in the bathroom) to henceforward be revoked. Respect your parents and they will respect you.
