This is what I suspect as well. Having been a teen, it seems very likely that a later start time wouldn't help some people who would just stay up later. Now may

This is what I suspect as well. Having been a teen, it seems very likely that a later start time wouldn't help some people who would just stay up later. Now maybe not as many people would do that, but then the issue is more that they just need to turn off the lights and go to sleep earlier. With great power comes create responsibility. Artificial light is a powerful thing when it comes to messing with natural sleep rhythms.