I think reclassing is much less common at day schools. A kid who is academically capable but immature faces a whole different set of challenges living in a dorm with more mature kids than one going home every night.
Also, reclassing within the community you have been in – which is part of the day school experience – if far tougher than starting in a whole new group as a reclassed student.
It’s often hard for students to imagine themselves reclassing for this reason – they imagine all their peers advancing a grade while they hang back. Agh! But when you’re not with that cohort, it doesn’t matter.