My 8-year old goes to bed at 8pm, with rare exceptions. My 14yo goes to bed by 9 latest, with rare exceptions. HOWEVER I have the right and responsibility to get either or both of them into bed earlier when I know they're tired. As an educator and parent, I know that teens actually NEED MORE sleep than when they're 8-10 years old. The tremendous changes they're going through really tax them. As a teacher, a HUGE problem is tired students!! Who don't eat breakfast! It drives me crazy.
So, at least 2x a week my 14yo goes to bed at 8. When I see him yawning and 'too tired' to do his chores, off he goes- and conks out right away. At times my 8yo is in bed at 7. We get up by 6:20 or so, and I have noticed that we all function much better when we're well rested. We need more sleep in the wintertime, too.
When I was a young mom, I was much more easy-going about bettimes, and a lot of things. In the last few years I have come to accept that the more structured approach really does our family good. Not only is everyone well-rested (and rarely ever get ill really!) but I know that my focus is almost 100% on my boys until 8-9, and then I get my time. It helps keep me balanced.