My brother in law is tired of his ex moving all the time and their kids have to change schools again. ?

They are 7 and 9 and have moved 11 times since they were born. Is there a law to give the child security? does the father have any say? I think my sis and BIL are frustrated. They went to open house for one of the kids yesterday and the mom tells the teacher they will be attending another school after 2 weeks.