Your kids are getting older, and you've found that they are having a harder time with the custody plan you have in place. Today, they went to school, for example, and the custody plan said that they'd come home and you'd be able to take care of them. Then, your tween called and said they wanted to go to their other parent's house and that their friend was having a sleep over nearby.
You want to be flexible with your custody plan, but when there are always changes like this (and they are happening more and more often), you feel like something needs to be altered. One option you and your ex-spouse discussed is changing who has custody through the school year, since your children have more friends near the other parent's home. That would also give you an opportunity to work more. Your ex-spouse is onboard with the idea, too, because your children are old enough to go to school on their own in the morning, so they can simply go to work a few hours earlier and be home for them. Even if your children missed the bus, the neighbor next door is a school teacher and said that they'd make sure they got there.