Once we realized that our kids understood what was said at the meetings, Me and my wife took the choice to stop attending. It just didn't make sense to raise our kids to see themselves as complete outcasts from the world (including school) believing that they have the ultimate truth while all others will perish.
Even though we stoped young, they had enough time at the meetings to tell me stuff like:
"I want to go to the meetings cause I want to be good, I don;t want to be evil".
In the ears of a JW, this is sweetness. In my ears, it sounded like:
"The whole world, 7+ Billions are evil cause they don't go to our meetings. I don't want to be evil with them."
It sent chills down my spine I swear.
On the otherhand, a whole lot of what is teached at the meeting is also good. So, if your kid is forced to go there, try to spend the equal amount of time sorting through the good and the bad and try to teach him how to think for himself and uphold his own convictions. In the end, nothing is black and white.