Have kids schedule how they are going to use their time throughout the day or (for MS and HS students) week. Scheduling one's time provides structure, empowers the learner, increases the likelihood of focus, and can shift responsibility from the parent to the student. It also builds executive function.
With younger children, just start with a schedule that outlines when they should engage in what activities. This could offer a daily structure for the week, as it would not indicate specific activities as much as topics. As they succeed at that, you can then include them in developing the next weekly schedule, giving them the choice to move items around. For example, your child might prefer to read in the afternoon than the morning.
This example shows how a mom of three set up a differentiated schedule to support each of her kids' different needs.
Older students can create schedules for themselves. It is so important to have them include both the start and end time. Let them attempt to map out the day ... they'll be so busy trying to follow their schedule that you'll be able to grab a cup of coffee rather than managing them!
Self-management is both an executive function skill and a social and emotional learning skill. At the end of each day, kids should reflect on how they did! What caused them to go off schedule? How were they able to stay on schedule? Don't make this a stressful structure; students can also learn the importance of flexibility as they move things around for good reasons. It's never meant to be punitive, but reflecting on one's day allows you to build insights into your own self-management abilities. And if you want to have more fun, schedule your day, too! That way you can model that reflection at the end of the day!