Private schools can get rid of chronically disruptive students. Public schools do not have that luxury.
That does not completely explain the difference in scores, of course. But it is big part of the explanation. Nevertheless I won’t let public schools off the hook. Public schools CAN develop ways to deal with chronically disruptive students. But that would take a measure of courage, something that most public school administrators just don’t have.
Public schools segragate continually disruptive students in special schools......Alternative HS etc....
Not a factor especially in the lower grades.....