|Trust is a two way street. With children, trust is earned not just granted. This is called parenting.|
I made it very clear to my children that computer usage was a privledge not a right. I would also check up on them when ever I wanted.
I would remote into my home router from work and review the logs to know if they were on and where they were going. I also did content filtering along with sending me an email. My son only tried once going to a porn site. If he wasn't scared straight from the netgear site blocked message popup then when I came home and talked to him about it certainly gave him a wake up call.
There are a number of parental monitoring softwares out that that are not detectable or removable by your children. They also give you a number of control/monitoring options.
This appears to be a really good one.