You have two children. One is still in elementary school, but your older child is in their last year of high school. They've always gotten along well, and you know that your older child has a good head on their shoulders.
When you and your spouse decided to divorce, your initial thoughts were to wait until your older child was in college. You would also wait until your younger child had graduated elementary school, so that switching schools wouldn't be as much of a problem if it needed to happen.
Both you and your spouse have been working hard to come up with solutions that work for both children, but their schedules vary wildly and you're not sure about what your older child would prefer. You don't intend to give your younger child a choice, because they aren't old enough, but for your senior in high school, it makes sense to you to allow them the opportunity to make their own decisions.
How old is old enough for children to choose their own custody schedules?
There is no easy answer to that question. Children are different. If your children are mature at 10 or 12, then you may want to ask their opinion. If they're nearly grown and out of the house, then they may need the independence to make decisions on their own. Legally speaking, the court will generally consider your child's preferences if they have any. There is no specific age limit.
You're right in thinking that an older child may need more say in the custody schedule they're given. If your teen is planning on living at home during college, this will be more of a concern than if they are going to be living in a dormitory. So, the first thing to talk to them about is what they think they would like to do.
Remember, the divorce may come as a surprise to them, and they may be reluctant to choose between either parent. In that case, you can have a schedule ready to suggest. For instance, if they'll return home on the weekends, ask them to come to your home every other weekend. If they'll live at home, consider having them switch weeks or come to the home with your younger child on the weekends, so that the weekly school night activities don't interfere with college studies or activities.
Every family is different. Your parenting plan should address these issues and make sure you and your spouse are satisfied with the decisions you make before you divorce.