A common criticism of home schooled children, and sometimes Christian schooled children, is that they are too sheltered - they do not know enough about the world around them. When they get out from under their parent's roof, they are more likely to fall prey to the temptations of alcohol, drugs, and sex because they were sheltered from the world rather than exposed to it. Since these temptations are new to them, they are more likely to give into the temptations. I think that such thinking is wrong and unbibilical.
In Romans 16:19, Paul expresses one of his goals for the Believers. He wants them to be "wise as to what is good and innocent as to what is evil." Our children will not be innocent as to what is evil if we expose them evil. I have heard of Christian parents who encourage their children to drink alcohol, even when they are underage, so they can learn how to handle it. Some parents purposefully expose their children to immoral music videos so they will know what is out there. They allow their children to be exposed to immoral lifestyles on t.v., music, magazines, and books because everyone else is doing it. Such exposure is contradictory to Romans 16:19 and keeping children innocent. Instead of exposing children to such evil, a parent's duty is to protect them from such evil.
This protection aligns with Philippians 4:8, where we are instructed to think about whatever is true, honorable, just, pure, lovely, commendable, excellent and worthy of praise. We should be replacing evil influences with godly influences as described in Philippians 4:8. By doing so, you are protecting your child's innocence from evil. At the same time, focusing on the good described in Philippians 4:8 helps satisfy the first part of Romans 16:19, "be wise as to what is good." We should fill ourselves up with things that are good and avoid evil. That is the Biblical command.
Some claim that being innocent as to what is evil results in being naive. This is not necessarily true. Paul even notes, in verse 18, that false teachers deceive those who are naive. You can prevent your children from being naive by warning them of the dangers of this world and explaining how Satan is like a roaring lion seeking to devour them. In Romans 16, the people would not be deceived if they had a strong foundation in truth. A good tactic is to warn against sin, but overload children with goodness.
I do not apologize for "sheltering" my children. They are better off by not being exposed to all of the evil in this world. Instead, we have emphasized the good and try to keep then immersed in goodness. At the same time, we have taught them about evil, warned them about sin, and discuss temptation. Then we return to filing their lives with goodness. If their lives are filled with goodness, then, hopefully, there is little room left for sin.