A 14 year old should go to bed at 8:00 PM so that they can wake up by 7:00 AM to catch the bus for school or walk to school.
A 14 year old needs around 10 to 11 hours of sleep per night for health and to keep them alert the next day.
So make sure the 14 year old gets into bed by 8:00 PM or 9:00 PM at the latest or they will be too tired to function the next day.
Some 14 year olds will try to stay up later than they should and then be tired the next day.
I was guilty of this same thing as well.
I would stay up late as a teen and then have a hard time functioning the next day.
Now that I go to work I make sure I sleep enough so that I'm alert the next day.
Not sleeping enough also makes you feel awful so make sure you get enough sleep.