In Amish communities?
The reason I have my doubts is that with the ubiquity of electronic access, combined with the fact that kids are inherently geared to learn new things such as technology (there are ways around filters using anonymous proxy routers if you know how to use them, which you can find in 10 seconds on Google - the only downside is the site may load a few seconds slower), means that parents are often behind the eight ball. Back in high school, my school paid for a ridiculously expensive network administration system through Nortel but a group of students used a keystroke logger to get the passwords that were needed. Most never cheated on anything in their life, but it was more about the challenge of being told to do something that the teachers bragged was impossible. It took about 2 days to get access to planning schedules, grade books, and emails. This was an enterprise system with a five-figure price tag that was beaten with a free, low cost hack.
(I mean, I've seen employers remove Internet Explorer entirely from a system to stop net access, thinking that would stop the problem, yet most younger people realize its built into the operating system so you can actually start browsing from any, boring desktop folder if you change the location to reference the http instead of the hard drive. This gets the system to launch a browsing session.)
You consider there is now Internet access at the local library, many new McDonald's, Starbucks, or Panera Breads, and it becomes quickly apparent that, unlike television in the older days, the Internet cannot be suppressed. A parent may make it inconvenient to access until 16 years old, but beyond that, it's going to be virtually impossible to stop a determined (and somewhat intelligent) teenager from seeing what he or she wants to see.
An interesting side note: What is probably most concerning is that several sociological studies show that the highest Internet pornography usage is among states with the highest proportion of traditional religion and the lowest among states such as California. The theory is that people want what they are told they can't have. It's the same reason we have 19 year olds in college die of alcohol poisoning and you don't see this happen in Germany. Here, alcohol is a forbidden fruit only for adults; there, it is something that even a child can have, in moderation, and they know the dangers of it. The stricter the limitations placed on people, the more they seek out and consume the forbidden thing when they get older and no one is around to see. You can read the study itself here.