Trying to share custody with your ex will be a challenge no matter what your circumstances are. If you have started living separately and are now in different states, things can be even more complicated. There will be jurisdiction issues and enforcement complications.
Unless both of you are very close to a shared state border, frequent custody changes may also be an unrealistic goal for interstate shared custody. Drive times could be prohibitive. In some cases, you may even need to arrange for the children to fly back and forth.
If you live far enough away to make weekly exchanges prohibitive, what are two of the ways you could make interstate shared custody work?
Alternating school years
If you want to share parental responsibilities as much as possible, the children can stay with one parent primarily for one school year and then the other for the next. Having them consistently enrolled in one school from fall to spring is more important than having them with one parent from January to January.
Extended visitation schedules
Sometimes, fully sharing custody is not realistic given the distance between households. The children might also struggle with switching between school districts.
If one parent will have the children every year for educational purposes, the other one could spend all of the major breaks from school with the children. They could even take the children for 3-day weekends if they live close enough. Otherwise, longer breaks from school like spring break, winter break and summer vacation could be spent with the parent living in another state.
Thinking about what will be best for you and the children can help you come up with a viable shared custody solution when you live in different states.