They are all of the age to yearn for independence. Just for that, I wouldn't warn them away from the society. Sometimes teenagers, you know, will end up doing the opposite. Just to prove they can.
Rather, I suggest you do all you can to encourage their ability to make up their own minds. Even if temporarily it digs them deeper in to the society. As you continue to honor their choices, NO MATTER WHAT THEY ARE, you will have earned their eternal respect. This will pay dividends for years to come.
You can also use directed, or Socratic questioning to help them come to their own conclusions. Also ask them to put themselves in your shoes, or to consider how others might feel about a decision. This again, reinforces their ability to reason. It also counteracts the Watchtower programming.
Once reason is released from the bounds of the Watchtower, there's no stopping them!