The average teenager should be getting 8-9 hours sleep per night and children should get between 9-11 hours, in order to best serve their bodies and minds. Along with that, a healthy diet to help them focus at school, with vitamin supplements if necessary, goes a long way.
Often, our children are so busy with extra-mural activities, that their only real time to study is in the evening. That being said, it is important to make sure that studying is effective, considering that this is the time when the “biological clock” says he/she should be asleep. This can cause a conflict with effective studying.
Sleep serves a critical role in our health and well-being and gives our body and mind a chance to rest, allowing it to prepare for the next day. While we are awake, our minds are barraged from input from 5 senses, as well as constantly using thought, logic, creativity, and creating memories. Sleep gives the brain the time it needs to sort out and store information that it has learned, replace chemicals and hormones, and solve problems.
The short answer to the question is that yes, children and teenagers should probably be studying during the day, but the evening may be the most peaceful time for them to focus without distraction. The effectiveness of their chosen study methods will reflect in their performance at school, but they may sometimes need you as parents (whether they agree or not) to put a limit on how much time they are staring at their books in comparison to counting sheep!
You might want to read about how sleep can improve athletic performance.
